Thin illumination system

ABSTRACT

The present invention introduces a new class of thin doubly collimating light distributing engines for use in a variety of general lighting applications. Output illumination from these slim-profile illumination systems whether square, rectangular or circular in physical aperture shape is directional, square, rectangular or circular in beam cross-section, and spatially uniform and sharply cutoff outside the system&#39;s adjustable far-field angular cone. Some embodiments provided include thin light distributing engines which provide input light collimated in one meridian and a light distributing element that maintains input collimation while collimating output light in the un-collimated orthogonal meridian, in such a manner that the system&#39;s far-field output light is collimated in both its orthogonal output meridians. The present invention can also include optical films that process the engine&#39;s doubly collimated output illumination so as to increase its angular extent one or both output meridians without changing beam shape or uniformity.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/864,857, filed Jul. 27, 2010, entitled “THIN ILLUMINATIONAPPARATUS,” which is a National Phase entry under of 35 U.S.C. §371 ofPCT/US2009/000575, filed Jan. 29, 2009, which claims priority under 35U.S.C. §119(e) to U.S. Provisional application U.S. Application61/024,814, filed Jan. 30, 2008 all of which are assigned to theassignee hereof. The disclosures of the prior applications areconsidered part of this disclosure and are incorporated by reference intheir entireties.

BACKGROUND OF THE INVENTION

The state of the conventional lighting fixtures used in commercialoverhead lighting applications around the world, from the lightingfixtures or luminaires routinely mounted overhead in traditional officeceilings to the many types and shapes of fixtures used in outdoor streetlighting, hasn't changed appreciably in a great many years. Standardlighting fixtures have remained typically large (24″×24″), thick(4″-10″), and weighty (7-30 lbs). The illumination they provide onsurfaces below them is often brightest directly underneath, falling offin brightness quickly as distance from the fixture's location increases.Even though a given lighting application may require illumination heldpredominately to a limited geometric area (e.g. table top or work area),nearby viewers still receive unwanted glare when looking upwards at thefixture's physical aperture. While some conventional fixtures have beendesigned for limited-angle spotlighting purposes, they typically achievenet illumination efficiencies far lower than desired from a modernenergy conservation perspective. Some light, is wasted by misdirectionoutside the area of interest, and other light, by the inefficiency thedeliberate physical baffling added to block glare, which also addssignificantly to the fixture's mechanical bulkiness.

A wide range of prior art has associated been with improvements in oneaspect or another of the various lighting characteristics of this broadclass of conventional lighting systems (e.g., fluorescent troffers andrecessed quartz-halogen or metal halide down lighting cans). Whilemodest gains have been made in luminaire efficiency, uniformity ofillumination, and glare reduction, to mention a few, the lightingfixtures themselves have still remained as bulky and imposing as ever.

The net weight of conventional lighting fixtures is too heavy for moststandard commercial ceiling frameworks without costly and cumbersomemechanical reinforcements. The heaviest lighting fixtures in mostindustrial applications need be suspended from the building's structuralutility ceiling, rather than from its more convenient decorative one,unless the decorative one is reinforced substantially. Even in the caseof the lightest weight conventional fixtures, reinforcing guide wiresneed be added to provide the extra mechanical support.

Conventional recessed lighting fixtures are also quite thick, which addsto the overhead plenum space required above the decorative ceiling toaccommodate them, thereby reducing the effective ceiling height. Ceilingheight reduction is particularly an issue in high-rise buildings whereceiling height is already limited by the building's structural boundaryconditions.

Recently, commercial lighting fixtures utilizing assemblies of miniaturelight emitting diodes (LEDs) have started to appear in earlyapplications featuring lighter more compact packaging. While this trendpromises still greater lighting fixture advantages over time, earlydevelopments have yet to realize the full potential.

One reason the early LED lighting fixtures have lagged in achieving thecompactness they promise is a consequence of their enormous brightnesscompared with that of the traditional light bulb alternatives. Lightemitted by LEDs is created in very small geometric regions, and as aresult, the associated brightness (i.e., lumens per square meter persolid angle in steradians) can be extremely hazardous to human viewwithout additional packaging structures added to block, restrict ordiffuse direct lines of view. One early solution to the LED's dangerousbrightness levels has been to hide them from view in lighting fixtures,whose light is reflected indirectly upwards off wall and ceilingsurfaces. While this approach prevents accidental view of the LED'sdirectly, the associated fixtures are as bulky as conventional ones.Another solution involves diffusing the LED light over a larger outputaperture. While this approach moderates aperture brightness infloodlighting applications, it does so at the expense of the fixture'sthickness, and while also increasing the fixture's propensity foroff-angle glare.

Looking at a bare LED emitter, even one combined with a reflector or alens, is a quite unpleasant experience, typified by temporary blindnessand a remnant image lasting minutes or longer. One of the most powerfulof today's newest commercial LED emitters generates about 300 lumens ina 2.1 mm×2.1 mm emitting region. This is a brightness of 20 millionCd/m² (nits). Such brightness appears more than 65,000 times as brightas the background brightness of the typical LCD display screens used inmodern desktop computer monitors. Such brightness also appears to be 200times brighter than the 18″ diameter aperture of commercial lightingfixtures using 250 W Hg arc lamps, which are already bright enough tocause viewers to see spots.

Modern LED light emitters require specialized lighting fixtures thatcapitalize on the LED's compactness potential, while providing a safeand desirable form of general illumination.

One of the more promising LED lighting adaptations involve a prior artLED illumination method, the so-called LED backlight. LED backlights arefinding more frequent use as the source of rear illumination for the LCDscreens used in large-format computer monitors and home televisions. Theemerging LED backlights involved are about 1″-2″ thick and spread lightfrom hundreds of internally hidden LED emitters uniformly over theirscreen area. By spreading and homogenizing the LED light emission, theLED backlight package thereby hides direct visibility of the otherwisedangerous brightness levels imposed by the bare LEDs themselves.

LED backlighting systems could be applied directly, for example,replacing the traditional 24″×24″×8″ fluorescent troffer in overheadoffice ceilings with significantly thinner and lighter weightalternatives.

As welcome as this possible LED lighting approach might be to commerciallighting use, the resulting fixture or luminaire is still a relativelythick and obtrusive one, veiling glare from its naturally wide angleemission remains an open issue, and beaming its output glow to limitedtask areas, is not provided. And while thinner than conventional lightbulb based lighting fixture, LED backlights are still too thick to beconveniently embedded within the body of typical building materials suchas ceiling tiles and wall board.

The light distributing engines of the present invention addresses allthese needs by introducing a new class thin plate-like illuminationsystems (also, luminaires and lighting fixtures) whose square,rectangular and circular illuminating beams are distributed uniformlyover enlarged output apertures of reduced brightness, while remainingsharply defined and well-directed in their illuminating extent from+/−5- to +/−60-degrees in each meridian, including all asymmetriccombinations in between. Such light engines satisfy a wider range ofgeneral lighting services than any of the known alternatives, includingwide area lighting, spot lighting, flood lighting, task lighting, andwall washing.

Semiconductor light emitting diodes (or LEDs) are chosen for allpractical examples of the present invention because of their intrinsiccompactness, because of their rapidly improving light generatingcapacity, and because of their increasingly low cost commercialavailability. Over time, other suitable luminaire types may emerge basedon organic LEDs (referred to as OLED), thin flat fluorescent sources,and flat micro plasma discharge sources, to mention a few.

While LEDs generally satisfy the present invention's need for thinness,applying LED light sources in accordance with the present inventioninvolves a degree of adaptation for best mode usage. The presentinvention describes light distributing engines comprising commercial LEDemitters with appropriate heat extraction means, associated opticalcouplers, associated light distributing optics, and when required,associated light spreading elements, all along with the low voltage DCpower control electronics needed to achieve preferable sources offar-field illumination whose cross-sectional thickness is less thanabout 1-inch. Moreover, the new light distributing engine configurationssafely dilute the LED's dangerously high brightness levels, withoutlosing any of its other favorable lighting characteristics, such astightly controlled beams of illumination and well-defined illuminationpatterns.

The light distributing engines of the present invention enableluminaires notably more compact in their physical size (approximately2.5″×2.5″) and especially thin in their cross-section (approximately5-10 mm). Though small in size, lumen outputs provided by these newlight distributing engines range from hundreds of lumens per luminaireto thousands. And the resulting output illumination is constrained tobeams organized as tightly as +/−5-degrees, as broadly as +/−60-degrees,or as any asymmetric combination in between—each with a sharp enoughangular cutoff to reduce off-angle glare (i.e., veiling glare) alongwith the spatially-even square, rectangular and circular far-fieldillumination patterns sought by lighting architects and users alike.

Some best mode examples of practical applications incorporating thepresent thin illumination system inventions have been represented inU.S. Provisional Patent Application Ser. No. 61/104,606, DistributedIllumination System. Extended practical applications of the presentinvention in this reference involve more detailed system examples of theease with which these thin illumination systems (also called luminairesand light distributing systems) may be incorporated within the physicalbody thickness of common building materials (as are used in formingcommercial ceilings and walls), electrically interconnected, andelectronically controlled (individually and as an interconnecteddistribution).

SUMMARY

It is, therefore, an object of the invention to provide a compact andslim-profile means of overhead LED illumination for commercial lightingapplications having a prescribed degree of angular collimation in eachof its two orthogonal output meridians and a square or rectangular farfield illumination pattern.

It is another object of the invention to provide a compact andslim-profile means of overhead LED illumination having its degree ofangular collimation modified in each of its two orthogonal outputmeridians by angle-spreading located in its output aperture thatmaintain the illumination systems rectangular far field illuminationpatterns.

It is a further object of the invention to provide a thin edge-emittinginput light engine using a single LED emitter whose output light iscollimated in one meridian and not in the other, working in conjunctionwith the input edge of a light guiding plate subsystem that preservesand transmits the collimated input light with out change in angularextent while collimating un-collimated input light, so that its outputlight is collimated in both output meridians.

It is also an object of the invention to provide a thin edge-emittinginput light engine using an array of single LED emitters whose outputlight is collimated in one meridian and not in the other, working inconjunction with the input edge of a light guiding plate subsystem thatpreserves and transmits the collimated input light with out change inangular extent while collimating un-collimated input light, so that itsoutput light is collimated in both output meridians.

It is still another object of the invention to provide a thinedge-emitting input light engine using a single LED emitter whose outputlight is collimated in one meridian and not in the other, working inconjunction with the input edge of a tapered light guiding platesubsystem that preserves and transmits the collimated input light without change in angular extent while collimating un-collimated inputlight, so that its output light is collimated in both output meridians.

It is yet another object of the invention to provide a tapered lightguiding plate subsystem that receives input light along its input edgeand uses a specific arrangement of reflecting facets and associatedoptical films laminated to a plane face of the tapered plate so that thetapered light guide plate subsystem is able as to collectively extract,collimate and redirect a square or rectangular beam of output light intothe far field.

It is further an object of the invention to provide a one-dimensionallyoperating angle spreading lenticular lens array film whose paraboliclens shape enables unique far field characteristics compared with priorart results.

It is still an additional object of the invention to provide for use oftwo orthogonally oriented one-dimensionally operating angle-spreadinglenticular array films having parabollically shaped lenticules able toconvert symmetrically collimated light input into either symmetricallyor asymmetrically widened output light having square or rectangular beamcross-section and the ability to create square or rectangularillumination patterns.

It is yet further an object of the invention to provide for the use oftapered light guiding plates whose cross-section has been extrudedlinearly forming square and rectangular tapered light guiding plateswith flat plane input edges.

It is still yet further an object of the invention to provide for theuse of tapered light guiding plates whose cross-section has beenextruded radially forming circular tapered light guiding plates havingcylindrical light input edges at the center of the circular plates.

It is yet an additional an object of the invention to provide for theuse of tapered light guiding plates whose cross-section has beenextruded both radially and linearly so as to form square and rectangulartapered light guiding plates having cylindrical light input edges at thecenter of the square or rectangular plates.

It is still one other object of the invention to apply lenticularfilmstrips to the input edge of light guiding plates for the purpose ofwidening the angle extent of an illumination system's output light inone meridian and not in the other.

It is still another object of the invention to apply geometricallyshaped portions of lenticular filmstrips to the input edge of lightguiding plates for the purpose of widening the angle extent only in alocal region of an illumination system as a means of improving nearfield brightness uniformity.

It is yet one other object of the invention to deploy thin-profileillumination systems with symmetrically and asymmetrically collimatedlight for the purpose of lighting a specific work task or work area.

It is additionally an object of the invention to deploy thin-profileillumination systems having oblique illumination beams withsymmetrically and asymmetrically collimated light for the purpose oflighting a specific wall mounted object, or for the purpose of providinga wash of light over a selected region of a wall.

It is yet an additional object of the invention to provide athin-profile illumination system whose aperture brightness has beenmoderated by spreading light over an enlarged area, while doing sowithout compromise in the sharpness of angular cutoff displayed by theilluminating beams that are produced.

It is a further object of the invention to provide a thin-profileillumination system whose aperture brightness has been moderated byspreading light over an enlarged area, while doing so without compromisein the square-ness or rectangularity of the field patterns that areproduced.

It is yet a further object of the invention to provide a thin-profileillumination system whose illumination remains largely within fixedsquare or rectangular angular beams as a means of reducing off-angleglare visible from below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a perspective view of a thin profile illuminationsystem containing two interconnected subcomponents, an edge-emittinglight bar input engine using a single LED emitter and a light guideplate that outputs a beam of square or rectangular collimated light fromone plate surface.

FIG. 1B contains an exploded view of the illumination system illustratedin the perspective view of FIG. 1A.

FIG. 1C provides an additional degree of explosion for the illuminationsystem illustrated in FIG. 1B, adding perspective views of light outputfrom the edge-emitting input bar and of the light output from the systemas a whole.

FIG. 1D contains a perspective view of the illumination systemillustrated in FIG. 1A, with the addition of two angle-spreading lenssheets beneath the lighting guiding plate to process the outgoing beamprofile in one or both output meridians.

FIG. 2A illustrates a perspective view of a thin profile illuminationsystem segment containing two interconnected subcomponents, one anedge-emitting input engine using a single LED emitter as input and acorrespondingly single angle-transforming reflector as output, placed inconjunction with a rectangular version of the general light guide plateillustrated in FIG. 1A, that outputs a square or rectangular beam ofcollimated light from one plate surface as shown.

FIG. 2B illustrates a linear array of four thin profile illuminationsystem segments as shown in FIG. 2A.

FIG. 2C illustrates a perspective view of a thin profile illuminationsystem containing two interconnected subcomponents, an edge-emittingarray-type input engine using a multiplicity of LED emitters as inputand a multiplicity of angle-transforming reflectors as output, placed inconjunction with the same light guide plate illustrated in FIG. 1A thatoutputs a square or rectangular beam of collimated light from one platesurface as shown.

FIG. 2D provides an exploded perspective view of the output edge of theedge-emitting array-type input engine illustrated in FIG. 2A, includinga perspective representation of the engine's output light collimated inone meridian, and not in the other.

FIG. 2E contains the illumination system illustrated in FIG. 2A, withthe addition of two angle-spreading lens sheets beneath the lightingguiding plate to process the outgoing beam profile in one or both outputmeridians.

FIG. 3A illustrates a perspective view of a thin profile illuminationsystem containing two interconnected subcomponents, a taperededge-emitting light bar input engine using a single LED emitter and atapered light guide plate that outputs a beam of square or rectangularcollimated light from one plate surface.

FIG. 3B contains an exploded view of the illumination system illustratedin the perspective view of FIG. 3A.

FIG. 3C contains an exploded perspective view of the LED emitter, therectangular angle-transforming reflector, and the input aperture of thetapered edge-emitting light bar input engine.

FIG. 3D provides an exploded perspective view isolating on therectangular angle-transforming reflector, and the input aperture of thetapered edge-emitting light bar input engine, including a the light coneinvolved.

FIG. 3E illustrates in exploded schematic cross-section the relationshipbetween the elements shown in FIG. 3D, including the simulated angularlight distributions developed in between them.

FIG. 4 provides a top view of the thin-profile illumination system ofFIG. 3A illustrating the dimensions and their relations to each other.

FIG. 5A illustrates in schematic cross-section the side view of atapered light guide pipe or plate, showing the corresponding angular farfield profiles of both input and output light beams.

FIG. 5B provides graphic profiles of the associated near field spatialuniformity developed on the tilted topside output face of the taperedlight guide of FIG. 5A.

FIG. 5C provides graphic profiles of the associated near field spatialuniformity developed on the flat bottom side output face of the taperedlight guide of FIG. 5A.

FIG. 6A illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide.

FIG. 6B illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide,choosing a slightly different start trajectory than the one shown inFIG. 6A.

FIG. 7A shows the effect on light extraction by adding a tiltedreflecting plane in air just above the tilted surface of the taperedlight guide illustrated in FIG. 5A.

FIG. 7B shows the effect on light extraction by adding a flat reflectingplane in air just below the flat surface plane of the tapered lightguide illustrated in FIG. 5A.

FIG. 7C shows the effect on light extraction by adding a tiltedreflecting plane that is optically coupled to the tilted surface of thetapered light guide illustrated in FIG. 5A.

FIG. 8A is a perspective view illustrating the single LED light emitterserving as the input portion of the double collimating lightdistributing engine examples of FIGS. 3A-3B and 4, as seen from itsoutput edge for the special case where its light extracting prismsfacets have collapsed to the unstructured form of a smooth mirror plane.

FIG. 8B provides a topside view of the edge-emitting LED light emitterof FIG. 8A, showing the obliquely directed far field beam cross-sectionthat results.

FIG. 8C provides a front view illustrating the light beam cross-sectionthat is emitted from the output edge of the system of FIG. 8B.

FIG. 8D illustrates the LED light emitter of FIGS. 8A-8C in a topsideperspective view showing the highly asymmetric nature of its obliquelydirected output illumination.

FIG. 9 illustrates the side cross-section of a tapered light guidingpipe (or plate) whose tilted (taper) plane is modified to include anoptical film stack having two different dielectric layers and a planemirror, also containing a superimposed simulation of the extractedoutput light's angular cross section.

FIG. 10 provides a graph detailing the quantitative relationship betweenthe angle of light extraction and the prevailing refractive indicescausing it.

FIG. 11A illustrates optical behavior in the side cross-section of atapered light guide structure similar to that of FIG. 9, but having aprismatic mirror plane composed of more steeply tilted mirror sections.

FIG. 11B provides a magnified side cross-section of a portion of theprismatic mirror plane of FIG. 11A.

FIG. 11C illustrates in schematic cross-section, the results of anoptical ray-trace simulation of light transmission within the taperedlight guiding structure of FIGS. 11A-B.

FIG. 12A provides an exploded perspective view of the edge-emittinginput engine that is a part of the illumination system of FIGS. 3A and4.

FIG. 12B provides a top view of the edge-emitting input engine that is apart of the illumination system of FIGS. 3A and 4, illustrating thecollimated output beams that are produced both just inside the lightguiding pipe comprising it, and as output in air.

FIG. 12C is a perspective view showing the edge-emitting output apertureof the edge-emitting input engine described in FIG. 12A showing aperspective view of the output emission that is well-collimated alongthe edge of the engine and significantly wider angled in the orthogonalmeridian.

FIG. 12D provides yet another perspective view of the engine of FIG.12A, this one containing a visualization of its coarse near-fieldspatial uniformity.

FIG. 12E illustrates still another perspective view of the engine ofFIG. 12A containing a visualization of its improved near uniformityassociated with its higher density of light extracting prism facets.

FIG. 12F represents the light distribution shown in FIG. 12D occurringon the output edge face of the input engine of FIG. 12A, when its lightextracting prism facet spacing is relatively large.

FIG. 12G illustrates the light distribution shown in FIG. 12F occurringon the output edge face of the input engine of FIG. 12A, when its lightextracting prism facet spacing has been reduced, but is still visible tohuman vision.

FIG. 12H illustrates the light distribution occurring on the output edgeface of the input engine of FIG. 12A, when the spacing of its lightextracting prism facets has been reduced, to dimensions not visible tohuman vision.

FIG. 13A is a perspective view showing the adverse effect a verynarrow-angle input source of light has on near field spatial uniformityalong the length of the engine's output edge.

FIG. 13B is a perspective view showing the beneficial effects awider-angle source of input light has on the near field spatialuniformity along the length of the engine's output edge.

FIG. 13C is a perspective view showing the adverse effects on near fieldspatial uniformity along the length of the engine's output edge whenusing an input source distribution with too large an angular range.

FIG. 14A is a graphic representation of one particularly narrow-anglelight distribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 14B is a graphic representation of a slightly wider narrow-anglelight distribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 14C is a graphic representation of an appropriately wide-anglelight distribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 14D is a graphic representation of too wide an angular lightdistribution provided as input to the light guiding pipe of theedge-emitting input engine of FIG. 12A.

FIG. 15 provides four comparative graphics plots of the input enginesnear field spatial uniformity as a function of distance from the inputaperture of the light guiding pipe involved, each corresponding to theinput light distributions of FIGS. 14A-D.

FIG. 16A provides a perspective view of the dimensional relationsexistent between a thin-profile single-emitter tapered light guidingillumination system, in its single-emitter form of FIG. 3A, elevatedabove a far field surface area to be illuminated.

16B provides a magnified perspective view of the tapered light guidingillumination system as its shown in FIG. 16A.

FIG. 17 is a graphic representation of the far field illuminationpattern made on the surface illuminated in the perspective view of FIG.16A.

FIG. 18 is a graphic representation of a set of differently tilted farfield beam cross-sections generated by the illumination system of FIG.16A in response to five slightly different choices of facet angleswithin the prisms applied to the surface of its tapered light guidingplate.

FIG. 19 is a graphic representation showing nine different far fieldbeam cross-sections to demonstrate the +60-degree to −60-degree range ofbeam directions that are accessible by means of varying internal lightredirecting prism angles within the thin-profile light guidingillumination system's plate.

FIG. 20 contains a graph of prismatic facet angles within lightextraction and turning film versus the far field beam-point angle itcreates, for the thin-profile light guiding illumination system of FIG.3A.

FIG. 21 is a side cross-section illustrating the computer ray-tracesimulated far field angle spreading behavior of a prior art form of bulkscattering-type diffusing sheet applied in the output aperture of thethin-profile light guiding illumination system of FIG. 3A.

FIG. 22A represents a schematic cross-sectional side view of a prior artform of a cylindrical lens array film containing spherically shaped lenselements known as a lenticular diffuser.

FIG. 22B provides a perspective view of the cross-sectional lenticularstructure shown in FIG. 22A.

FIG. 22C provides a topographic schematic perspective view of thepebbled surface morphology of a prior art angle spreading diffuser filmstructure containing mathematically developed two-dimensionaldistributions of micro-sized lens elements.

FIG. 23A shows the far field beam cross section that results when+/−5-degree×+/−5-degree collimated light as from the light emittingsystem of FIG. 3A is applied to the plane side of a lenticular lenssheet having spherically shaped lenticular elements.

FIG. 23B shows the far field beam cross section that results when+/−5-degree×+/−5-degree collimated light as from the light emittingsystem of FIG. 3A is applied to the lens side of a lenticular lens sheethaving spherically shaped lenticular elements.

FIG. 24A provides perspective view of a lenticular lens sheet structurehaving parabollically shaped lenticular elements.

FIG. 24B shows the round-bottomed far field beam cross section thatresults when +/−5-degree×+/−5-degree collimated light as from the lightemitting system of FIG. 3A is applied to the plane side of a lenticularlens sheet having parabollically shaped lenticular elements with arelatively shallow sag.

FIG. 24C shows the flat-bottomed far field beam cross section thatresults when +/−5-degree×+/−5-degree collimated light as from the lightemitting system of FIG. 3A is applied to the lens side of a lenticularlens sheet having parabollically shaped lenticular elements with arelatively shallow sag.

FIG. 24D shows the wider-angled round-bottomed far field beam crosssection with satellite wings that results when +/−5-degree×+/−5-degreecollimated light as from the light emitting system of FIG. 3A is appliedto the plane side of a lenticular lens sheet having parabollicallyshaped lenticular elements with a moderately deep sag.

FIG. 24E shows the wide-angle flat-bottomed far field beam cross sectionthat results when +/−5-degree×+/−5-degree collimated light as from thelight emitting system of FIG. 3A is applied to the lens side of alenticular lens sheet having parabollically shaped lenticular elementswith a moderately deep sag.

FIG. 24F shows the wide angle tri-modal far field beam cross sectionthat results when +/−5-degree×+/−5-degree collimated light as from thelight emitting system of FIG. 3A is applied to the plane side of alenticular lens sheet having parabollically shaped lenticular elementswith a very deep sag.

FIG. 24G shows the very wide angle far field beam cross section thatresults when +/−5-degree×+/−5-degree collimated light as from the lightemitting system of FIG. 3A is applied to the lens side of a lenticularlens sheet having parabollically shaped lenticular elements with a verydeep sag.

FIG. 25 is a graph summarizing the best mode geometric relationshipfound to exist between total far field angle and the paraboliclenticular peak-to-base ratios between 0.1 and 1.0, for lenticulardiffuser sheets.

FIG. 26 is a perspective view of the collimated thin-profileillumination system as depicted in FIG. 3A now containing a singleparabolic-type lenticular angle-spreading sheet below its outputaperture, the lenticular axes running parallel to the illuminator'sy-axis oriented input edge.

FIG. 27 contains a computer simulation of the rectangular far field beampattern produced by the illumination system of FIG. 26 on an 1800mm×1800 mm illumination surface from a height of 1500 mm; therectangular pattern stretched asymmetrically +/−30-degree along thesystem's x-axis.

FIG. 28 shows a perspective view of the collimated thin-profileillumination system as depicted in FIG. 3A containing two orthogonallyoriented parabolic-type lenticular angle-spreading sheets below itsoutput aperture, the lenticular axis of one sheet running parallel tothe illuminator's y-axis oriented input edge, and the lenticular axis ofthe other, running parallel to the illuminator's x-axis.

FIG. 29A contains a computer simulation of the square far field beampattern produced by the illumination system of FIG. 28 on an 1800mm×1800 mm illumination surface from a height of 1500 mm, the squarepattern symmetrically disposed +/−30-degrees along both the system's xand y axes.

FIG. 29B contains a computer simulation of the tighter square far fieldbeam pattern produced by the illumination system of FIG. 28 on an 1800mm×1800 mm illumination surface from a height of 1500 mm, the tightersquare pattern symmetrically disposed +/−15-degrees along both thesystem's x and y axes.

FIG. 30A provides an exploded top perspective view of one example of afully configured light engine embodiment of the present invention basedon the functional illustrations of FIGS. 1A-1D, 3A-3E, 4, 16A-16B, 26,and 28.

FIG. 30B provides a magnified perspective view of the coupling regionexistent between a commercial LED emitter that can be used, thecorresponding square or rectangular reflector and a tapered lightguiding bar with light extraction film according to the presentinvention.

FIG. 30C provides a perspective view of the completely assembled form ofthe fully-configured light engine embodiment shown in exploded detail inFIG. 30A.

FIG. 30D illustrates a related geometric form of the present inventionin which metal coated facetted layer may be replaced by a planereflector and a separate facetted light extraction element placed justbeyond the front face of pipe (facet vertices facing towards the pipesurface).

FIG. 30E is a perspective view showing the variation of FIG. 30D appliedto light guiding plate.

FIG. 31A provides an exploded top perspective view of a practical singleemitter segment following FIG. 2A for a fully configured multi-emitterlight engine based on a reflector-based means of input to a lightguiding plate.

FIG. 31B is a perspective view of the assembled version of the practicallight engine example shown exploded in FIG. 31A.

FIG. 31C is a schematic top view providing a clearer description of theunderlying geometrical relationships that are involved in matching LEDemitter, reflector and light guiding plate.

FIG. 32A illustrates a perspective view of a multi-emitter thinillumination system as was generalized in FIG. 2A-2E and FIGS. 31A-31Cshown without top reflector to reveal internal details.

FIG. 32B is illustrates a perspective view of the system in FIG. 30A,with top reflector added, also showing the system's down directed farfield output beam profile.

FIG. 33A shows a topside perspective view of two side-by-sidedown-lighting engine segments of emitter-reflector-light guiding platethin illumination system invention variation illustrated in FIG. 31B.

FIG. 33B shows a topside perspective view of two in-line down-lightingtwo-engine segments of the emitter-reflector-light guiding plate thinillumination system invention variation illustrated in FIG. 31B.

FIG. 33C shows a topside perspective view of two counter-posedtwo-engine segments of the emitter-reflector-light guiding plate thinillumination system invention variation illustrated in FIG. 31B.

FIG. 34A is a schematic perspective illustrating execution of the globalboundary condition for linear extrusion of the tapered light guidingplates introduced in the above examples.

FIG. 34B shows in schematic perspective that the linear boundarycondition of FIG. 34A also forms the linearly extruded facetted lightextraction films as were shown in the above examples.

FIG. 34C illustrates in schematic perspective a basic execution of theradially constrained extrusion to form disk-type tapered light guidingplates under the present invention.

FIG. 34D shows in schematic perspective the circular taperedcross-section light guiding plate that results from executing the radialextrusion illustrated in FIG. 34C.

FIG. 34E is a schematic perspective view illustrating the correspondingradial extrusion process for facetted cross-section sweeping about anaxis line and circular guide path to form a radially facetted lightextraction film according to the present invention.

FIG. 34F is a topside schematic perspective illustrating the radiallight extracting film that results from executing the radial extrusionillustrated in FIG. 34E.

FIG. 35A is a cross-sectional perspective view illustrating radiallyfacetted light extracting film of FIG. 34E and circular light guidingplate of FIG. 34D combined in accordance with the present invention.

FIG. 35B is a cross-sectional perspective view illustrating the internaldetails of one example of a practical combination of illustrative LEDemitter (as in FIG. 31A) with radial light guiding system of FIG. 35A.

FIG. 35C is a magnified view of the cross-section of FIG. 35B showingfiner details of the light input region of this illustrative radial formof the thin emitter-reflector-light guiding plate illumination system.

FIG. 36A is a partial cross-sectional perspective view revealinginternal details of the thin emitter-reflector-light guiding plateillumination system of FIG. 35A, but with an example of a radialheat-extracting element useful in such configurations.

FIG. 36B is a schematic perspective view of the illustrative lightengine embodiment represented in FIG. 36A, without the cross-sectionaldetail of FIG. 36A, and in a down-lighting orientation.

FIG. 36C is a schematic perspective view similar to that of FIG. 36Bshowing the illustrative light engine embodiment of FIGS. 35A-35C and36A-36B and it's intrinsically well-collimated far-field outputillumination.

FIG. 36D is an exploded perspective view of the light engine representedin FIG. 36B, adding parabolic lenticular film sheets and a circularframe to retain them.

FIG. 36E shows the unexploded view of the thin system of FIG. 36D.

FIG. 36F is a schematic perspective view similar to that of FIG. 36C butshowing the asymmetrically widened far field output illumination of thethin illumination system shown in FIG. 36E.

FIG. 36G shows the illustrative far field beam pattern from the thinillumination of FIG. 36F placed at a 1500 mm height above the 1800mm×1800 mm surface to be illuminated.

FIG. 37 is a schematic perspective view illustrating the thin profilelight engine example of FIG. 36E configured as screw-in style lightbulb.

FIG. 38A is a schematic perspective view of a square truncation of theradially constrained light guiding plate extrusion illustration shownpreviously in FIG. 34C.

FIG. 38B is magnified section view of the complete schematic perspectiveprovided in FIG. 38A, better illustrating the significance ofedge-thickening defects caused by premature truncation.

FIG. 39A illustrates a radially and linearly constrained extrusion withfive prototype taper cross-sections, swept in a 90-degree radial arcsegment about an axis line running parallel to system's Z-axis.

FIG. 39B is a perspective view illustrating the extrusive combination offour of the 90-degree segments as developed in FIG. 39A.

FIG. 39C is a perspective view, similar to that of FIG. 34D, butillustrating the quad-sectioned square tapered light guiding plate thatresults from the radially and linear constrained extrusion of FIG. 39C.

FIG. 39D is a perspective view of a thin square light engine form of thepresent invention that uses a square lighting guiding plate, and anotherwise similar internal arrangement to that of the circular lightengine example shown in FIG. 36E.

FIG. 40A shows a perspective view of another embodiment of thesingle-emitter form of the thin illumination system 1 deploying atapered light guiding pipe system as its input engine cross-coupled witha tapered light guiding plate system using a plane top mirror.

FIG. 40B is a side cross-sectional view of FIG. 40A.

FIG. 40C is a perspective view of the illumination system of FIGS.40A-40B showing the collimated nature of the obliquely directed farfield output beam the system produces.

FIG. 41A is a side elevation showing the illumination system of FIGS.40A-40C mounted 10 feet above ground level and a horizontal distance of3 feet from a vertical wall surface to be illuminated.

FIG. 41B shows a front view of an illuminated wall surface and the beampattern made by illumination system 1 of FIG. 41A.

FIG. 42 is a perspective view of an illumination system similar to thatof FIG. 40C, but including a one-dimensional angle-spreading lenticularfilmstrip on the input-edge the system's tapered light guiding plate towiden the outgoing beam's horizontal angular extent.

FIG. 43A illustrates the side elevation of a wall and floor includingthe illumination system of FIG. 42.

FIG. 43B shows a front view of the wall surface illuminated using theillumination system of FIG. 42, including the resulting beam pattern.

FIG. 44 is a side view of a thin profile illumination system embodimentbased on the illumination systems of FIGS. 40A-40C, 41A, 42 and 43Acombined with an external tilt mirror.

FIG. 45A is a side elevation showing the tilted-mirror illuminationsystem of FIG. 44 for a 12-degree tilt mounted 10 feet above groundlevel and positioned 3 feet from the vertical wall surface to beilluminated.

FIG. 45B shows a front view wall surface illuminated by the 12-degreetilted mirror illumination system of FIG. 44 and its associated beampattern.

FIG. 46A is a side elevation identical to FIG. 45A, but for the case ofa 16-degree mirror tilt.

FIG. 46B shows a front view wall surface illuminated by the 16-degreetilted mirror illumination system of FIG. 46A and its associated beampattern.

FIG. 47 is a perspective view of the corner of a room, showing its twowalls, a floor, and a framed painting illuminated obliquely by thethin-profile tilted mirror illumination system of FIGS. 44, 46A and 46B.

FIG. 48A shows a topside view similar to FIG. 42, adding aone-dimensional angle-spreading lenticular filmstrip to input edge ofthe system's light guiding plate to widen the outgoing beam's horizontalangular extent, using a prism sheet rather than a plane mirror atoptapered light guiding plate.

FIG. 48B shows the configuration of FIG. 48A in perspective view.

FIG. 48C is another perspective view of FIG. 39A, showing theillumination system's underside output aperture

FIG. 49 is a perspective view of the tapered-version of the lightguiding input engine 120, showing f angular extent of the light at thestart of the light guiding pipe, plus a graphic simulation sequence ofoutput light at various points along the pipe's output edge.

FIGS. 50A-50B, 50D, 50F and 50G all show perspective views of the slimprofile illumination system differentiated by the various lenticularfilm section configurations that have been simulated.

FIG. 50C shows a magnified view of the perspective of FIG. 50A.

FIGS. 50E and 50H show perspective views of two different near fielduniformity improvements.

FIG. 51A shows a side view of a schematic light extraction filmcross-section that underlies the concept behind a variable prism spacingdesign method, using conveniently enlarged prism coarseness.

FIG. 51B shows a perspective view of the design concept illustrated inFIG. 51A.

FIG. 51C shows a perspective view of a thin illumination system 1 of thepresent invention with successfully homogenized near field using thevariable prism-spacing method.

FIG. 52 shows a graphical comparison of near field spatialnon-uniformity of one thin profile illumination system partiallysuccessful angular input edge correction as in FIG. 41H and one with thecomplete correction illustrated in FIG. 42C via the variable-prismspacing-method.

DETAILED DESCRIPTION

An optical system 1 constructed in accordance with one principal form ofthe thin-profile illumination invention is indicated generally in theschematic perspective shown in FIG. 1A and in the exploded perspectiveshown in FIG. 1B. This form of the present invention collects the lightfrom a wide angle plane emitter (e.g., and LED), uses a thin lightguiding bar to provide a strong degree of collimation in one meridian,and then further processes this light with an equally thin light guidingplate that retains the strong degree of pre-collimation in the firstmeridian while adding an equally strong degree of collimation to thelight in a second meridian orthogonal to the first, so as to produce auniform source of doubly collimated far field output light from asignificantly enlarged output aperture. The light distributing engine 1so illustrated consists of two subcomponents, a light emitter 2(preferably an LED-based light emitter, or LED light emitter) whoseoutput light 4 is arranged to be redirected through output edge 8 intothe corresponding edge of an adjacent light distributing optic 9 whoseinternal design is arranged to transform incoming output light 4 intowell-organized output light 10 that's evenly distributed over the lightdistributing optic's significantly enlarged output aperture 11 in amultiplicity of overlapping beams across that aperture whose light conesare limited in angle to +/−θ₁, and +/−θ₂ in the light distributingengine's two orthogonal output meridians (e.g., the ZX meridian and theZY meridian). Light emitter 2, in this form, is preferably composed ofan edge-emitting light bar (equivalently, an edge-emitting light pipe,an edge-emitting light guide, or a light spreading pipe) 18 having asingle LED emitter 3 at its input, and an internal design arranged sothat the edge-emitting light pipe's output light 4 is distributed evenlyalong the length of its output edge 8, and pre-collimated more narrowlyin one meridian (e.g., ZY meridian inclusive of the plane common toY-axis 5 and Z-axis 6) than in the other (e.g., ZX meridian inclusive ofthe plane common to X-axis 6 and Z-axis 6). Light distributing optic 9,in this form, receives output light 4 from light emitter 2 along outputedge 8, and preferably comprises a transparent (dielectric) lightguiding plate 28 and associated light extracting and redirectingelements 34, whose internal design enables output light 10 to bedirected outwards (downwards as shown) from just one of its planeaperture surfaces 11, collimated in both output meridians (ZX and ZY asabove).

Orientation of parts, light directions and angular extents are relatedto the three orthogonal crystallographic axes 5, 6 and 7, Y, Z and Xrespectively.

As one example, LED light emitter 2, consists of a single LED emitter 3that may contain one or more LED chips within its output aperture (notillustrated), a coupling optic 14 that may be a rectangularetendue-preserving angle-transforming reflector (RAT) designed tocollect and transport light efficiently from emitter 3 to input face 16of transparent dielectric light guiding bar 18 with a pre-selectedangular distribution in each orthogonal meridian, separated from lightdistributing optic 9 by a thin air-gap 20. Transparent light guiding bar18 itself consists of two co-joined optical elements 22 and 24,transparent light guiding bar (pipe or guide) 22 having square (orrectangular) cross-section with smoothly polished sides (or edges) thattransmits input light flowing within by total internal reflection, andlight extracting film 24 placed adjacent to one edge of light guidingbar 22, whose detailed design and composition is explained in moredetail further below, extracts a fraction of the light flowing withinbar 22 striking it everywhere along its length, and thereby collimatesthat light in one meridian (Y, 5) without changing the angulardistribution of the extracted light in the other meridian (Z, 6), whileredirecting all extracted light uniformly over the bar's lengthsubstantially in an outwards direction through output edge 8 along thesystem's X axis 7.

Light distributing optic 9 also consists of two co joined opticalelements, one being transparent dielectric light guiding plate 28, andthe other being adjacent light extracting film 34. Light guiding plate28 has a flat and polished input edge 25, and two flat and polishedplane faces, 11 and 32. Light extracting film 32, in the example ofFIGS. 1A-1B is laminated to plane face 32. (In an analogous form, it maybe placed just beyond plane face 11.) Design and composition of lightextracting film 32 (described further below) enables a fraction of thelight striking everywhere along its length and over its area to be freedfrom total internal reflections within plate 28, collimated in onemeridian (X, 7) without change to the pre-collimated angulardistribution of light in the other (Y, 5), and redirected as adoubly-collimated output beam 10 heading outwards along the element'soutput axis 6 (Z) or some other output light direction at an angle toit.

There are three meridian planes of importance to the examples thatfollow. The horizontal meridian (for convenience also called the XYmeridian) is taken as the XY plane parallel to the large face planes oflight distributing optic 9. The first vertical meridian (for conveniencealso called the ZY meridian) is orthogonal to the horizontal meridian,and taken herein as the ZY plane parallel to input edge 25 of lightdistributing optic 9. The second vertical meridian (for convenience alsocalled the ZX meridian) is orthogonal to both the horizontal meridianand the first vertical meridian, taken herein as the ZX plane. TheCartesian system of reference throughout comprises Y-axis 5, Z-axis 6and X-axis 7.

FIG. 1C is a partially exploded perspective view that illustrates moreclearly the system's various light-flows and the corresponding angulardistributions created by the doubly collimating actions of the presentinvention. In general description, input light from LED emitter 3 iscollected by and passes through the input and output apertures ofcoupling optic 14, wherein its transformed to beam 36 having anoptimized angular distribution for coupling into input face 16 of lightguiding bar 18 along Y-axis 5. As beam 37 passes through the length ofbar 18, it is arranged to turn 90-degrees from Y-axis 5 to X-axis 7 bythe action of light extracting film 24, and is output everywhere alongedge face 8 as edge-emitted light beam 38, collimated strongly in thehorizontal XY meridian to angular width +/−θ_(Y) (in air) 40 and moreweakly as angular width 42 in the vertical ZX meridian. Light beam 38then couples through edge face 25 into the body of light distributingoptic 9 and its light guiding plate 28 as beam 39 directed along X-axis7. As beam 39 passes through the length and volume of light guidingplate 28, it turns 90-degrees everywhere from its initial propagatingX-axis direction 7 to it output Z-axis direction 6 as beam 45 by theaction of light extracting film 34. Beam 45 is collimated strongly inthe vertical ZX meridian narrowing to angular width +/−θ_(X) (in air) 41by its passage through light distributing optic 9, but retains itsequally strong pre-collimation +/−θ_(X) in plate 28 (+/−θ_(Y) in air) inthe horizontal ZX meridian as angular width 44. The result iswell-collimated far field output illumination 10 emanating into air fromthe surface area of plane face 11 of light distributing optic 9,illumination 10 being equivalently well-collimated in both outputmeridians, +/−θ_(Y) in the vertical ZY meridian (pyramidal face 46) and+/−θ_(X) in the vertical ZX meridian (pyramidal face 48).

Wide angle light beam 36 is output from coupling optic 14, in thisexample a rectangular etendue-preserving angle-transforming (RAT)reflector with an etendue-preserving angular distribution in each of itstwo orthogonal output meridians (XY and ZY) that's chosen to maximizethe efficiency of input coupling to input face 16 of transparent lightguiding bar 18 while also maximizing the spatial uniformity of outputbrightness produced along the length of the bar's output edge (or face)8. The light guiding bar's resulting far-field output beam 38 (shownsymbolically as a pyramidal solid) is well collimated in the horizontalXY meridian by action of the present invention, and as such achieves areduced angular width 40 (also referred to as a reduced angular extent),designated as +/−θ_(Y) (2 θ_(Y) full angle). Angular distribution ofoutput light 38 in the orthogonal ZX meridian is substantially unchangedby its passage through light guiding bar 18 and retains the originalwide angle input beam 36 characteristic of coupling optic 14 in itsvertical ZY meridian, in this case a RAT reflector. Angular cone 42 inthis vertical ZX meridian is arranged to achieve the most efficientoptical coupling of light passing from output edge 8 and into input edge25 of corresponding light guiding plate 9. Input angle 42 is also chosento achieve the highest spatial uniformity of the output light extractedacross the component's full output aperture surface 11, as will beexplained in more detail further below. As input light cone 38 entersthrough the input edge 25 of light distributing optic 9, it undergoestotal internal reflection within plate 28. The angular width of lightflowing in the plate's horizontal XY plane is represented symbolicallyby internal beam cross-section 43, and retains the angular extent 40 ofthe incoming light in this meridian. The angular relationship betweenthis horizontal light in the air surrounding light distributing optic 9and the corresponding light within in the medium of plate 28 is simplySin(θ_(Y))=n Sin(θ_(YY)) with n being the refractive index oftransparent light guiding plate 28.

Etendue-preserving RAT reflector 14 has an input aperture dimensioned d₁by d₂ (not illustrated) designed to match the output aperture of LEDemitter 3 (not illustrated), also dimensioned substantially d₁ by d₂.RAT reflector 14 has an output aperture that is D₁ by D₂. RAT reflector14 is four sided and with each reflector sidewalls mathematically-shapedto preserves etendue between input and output apertures, so transformingthe LED's wide angle output emission to etendue-preserving output lightthat then passes through the RAT reflector's output aperture in bothmeridians of the light guiding pipe (or bar) 22 with an angular extentsubstantially equaling +/−e, by +/−θ₂, where +/−θ₁ and +/−θ₂ aredetermined by the applicable etendue preserving Sine Law,θ_(i)=Sin⁻¹(d₁/D₁), where d₁ and D₁ refer to the input and outputaperture dimensions in each meridian, d₁ and d₂ (in spatial dimensions),D₁ and D₂ (in spatial dimensions) and θ₁ and θ₂ (in angular dimensions).

As will be established further below, the RAT reflector's most usefuloutput angles for maximum light coupling to the input aperture of thelight guiding pipe is best reduced to about 50-55 degrees in eachhalf-angle in air, i.e., +/−θ₁ and +/−θ₂. The design values for d₁, d₂,D₁ and D₂ will be adjusted accordingly, depending on the dimensions ofthe LED emitter 3 being used. The length or physical separation betweeninput and output apertures of RAT reflector 14, L, is substantially asprescribed by the Sine Law, L=0.5 (d_(i)+D_(i))/Tan θ_(i) with L beingthe larger of the lengths calculated in each of the RAT reflector's twomeridians, but may be foreshortened by 10% to 40% without significantpenalty in coupling performance.

Doubly collimated (or cross collimated) output light is distributeduniformly over the surface area of its output aperture 11 by thelight-distributing engine of system 1. The doubly collimated far-fieldbeam 10 is further represented in FIG. 1C by computer-simulated profile50 explained further below. When θ_(Y)=θ_(X), as in the present example,output beam 10 has a square cross-section. When θ_(Y)>θ_(X) or whenθ_(Y)<θ_(X), which is also possible, output beam 10 has a rectangularcross-section.

This particular form of the present invention is distinguished from allknown prior art, not only by the cross-sectional thinness achieved withthe combination of light emitter 2 and light distributing optic 9, butalso by virtue of the doubly-collimated output beam that results fromtheir collective optical behaviors, one degree of output beamcollimation coming from edge-emitting light emitter 2 and the orthogonaldegree of output beam collimation coming from the light guiding,extracting and redirecting nature of light distributing optic 9. Whilesome prior art examples of thin illumination systems have producedcollimated light in one output meridian and not in the other, only thepresent invention produces independently collimated light in bothorthogonal output meridians.

Doubly-collimated output beam 50 may be expanded externally to createany orthogonal set of output beam angles larger than +/−θ_(Y) by+/−θ_(Y′), as shown in the perspective view of FIG. 1D by adding one ortwo angle-spreading film sheets 52 and 53 just beyond output aperturesurface 11 of system 1. Such films are actually quite thin (preferably<0.250 mm), and add very little additional thickness to the lightdistributing engine's slim cross-section.

A special lenticular class of angle-spreading film sheets will beintroduced and described further below as an additional feature of thepresent invention. Such film sheets are applied to change (i.e., widen)the angular spread of light passing through them in only one meridianand not in the other. Orienting two such lenticular sheets with theirlens axes oriented substantially orthogonal to each other, as in FIG.1D, enables a complete family of wider far field beam patterns to beachieved, with a different angular width, 56 and 58, affected in eachmeridian. The lenticular sheets included within the present inventionare distinguished from all others in prior art by their ability topreserve the square and rectangular far field beam shapes (orillumination patterns) characteristic of these particular thin-profiledoubly collimating light distributing engines of illumination systems 1.If the far field output beam from system 1 in FIGS. 1A-1C is+/−5-degrees by +/−5-degrees and makes a substantially square far-fieldillumination pattern, just as one example, some possible far field beamalternatives 56 and 58 for the system of FIG. 1D are +/−10-degrees by+/−10-degrees, +/−5-degrees by +/−20-degrees, +/−30-degrees by+/−30-degrees, and +/−25-degrees by +/−15-degrees to mention but a few.When the expanded angular ranges are the same in each meridian, theresulting illumination pattern is substantially square. When theexpanded angular ranges are different in each meridian, the resultingillumination pattern is substantially rectangular.

Output beam angle spreading may also be achieved using more-conventionaldiffusing materials as have been described in prior art, such asspherical lenticular lens sheets and highly asymmetric light shapingdiffusers based on holographic (diffractive) principles. In neithercase, however, are the characteristic advantages of sharp angular cutoffmaintained nor are square or rectangular beam patterns achieved. The farfield output beam patterns obtained using conventional prior artdiffusers in the manner illustrated in FIG. 1D are either circular orelliptical in nature.

An optical system 1 constructed in accordance with a second principalform of this thin-profile illumination system invention is showngenerally in the perspective views of FIGS. 2A-2E. The principaldifference between this form of the present invention and the relatedform illustrated generally in FIGS. 1A-1D is that in this form the LEDlight emitter 2 provides strongly pre-collimated input light in onemeridian directly from the output of coupling optic 14 to the input edgeof light distributing optic 9, doing so without need of light guidingbar 18 as the pre-collimating intermediate. In this form, coupling optic14 is preferably a rectangular etendue-preserving angle-transformingreflector (RAT), whose collimating power is applied to narrow the LEDemitter's angular extent in the horizontal XY meridian to +/−θ_(Y) (inair) becoming +/−θ_(YY) in light distributing optic 9 upon coupling (asin angular extent 44 of coupled beam representation 43 as shown in FIG.2A). The RAT reflector's cross-meridian ZX is used as above, simply toprovide just enough collimation to optimize light coupling performance(efficiency and uniformity) with regard to light distributing optic 9.In this form, the width 60 of light distributing optic 9 (designated asW) approximately equals the XY meridian output aperture width 61 of RATreflector 14 (designated D₁), with D1 established by the classical SineLaw as approximately d₁/Sin θ₁, with d₁ being horizontal width 63 ofoutput aperture frame 62 of LED emitter 3 (which as mentioned earlier isd₁ by d₂ horizontally and vertically).

While a more detailed example of this form is provided further below, aninitial example is provided here to give scale to the generalizedillustration of FIG. 2A. When d₁=3.6 mm, which is one possibility, andwhen the XY meridian's pre-collimation is to be+/−θ₁=+/−θ_(y)=10.5-degrees, which is another possibility, D₁=19.75 mm,and the RAT reflector's ideal length 64 (designated as L) is also by theSine Law, 0.5(d₁+D₁)/Tan θ₁=63 mm, which as mentioned above, can beforeshortened by 10%-40% without serious penalty.

Cross-sectional thickness 66 of the light distributing engine 1 in FIG.2A (designated as T) is approximately equal to the RAT reflector'svertical output aperture dimension 67 (designated as D₂), which in turnis driven by vertical dimension 65 (designated as d₂) of the LED emitteroutput aperture frame 62. When d₂ is for example 2.4 mm, which isanother reasonable possibility, and when the desired collimating angleis +/−55-degrees, as explained further below, D₂, by the Sine Law,becomes d₂/Sin θ₂=2.9 mm, which emphasizes the potential thinness oflight distributing engines according to the present invention.

FIG. 2A is a partially exploded perspective view illustrating thegeneral constituents of this form of doubly collimating lightdistributing engine 1, which are LED emitter 3, coupling optic 14, lightdistributing optic 9, and doubly collimated output illumination 10,generally directed along (or at an angle to) Z-axis 6. Substantially allemitted light from LED emitter 3 is collected by the correspondinglysized input aperture of coupling-optic 14 preferably a rectangularetendue preserving angle transforming (RAT) reflector. Thensubstantially all collected light (less reflection and absorption losswithin the RAT reflector's 4-sided reflecting structure 68) is coupledfrom the reflector's rectangular D₁ by D₂ output aperture to thecorrespondingly sized rectangular input aperture of light distributingoptic 9. The in-coupled light is represented symbolically, as above, bypropagating beam 43, which has pre-collimated angular extent +/−θ_(YY)as shown within the horizontal XY meridian light distributing optic 9,but satisfies the boundary conditions of total internal reflection ateach of the light distributing optic's four external surface boundaries.Then, as explained generally above, doubly collimated outputillumination 10 emanates uniformly over the surface area of outputaperture plane 11 as a result of pre-collimation in the horizontal XYmeridian and interactions between propagating light 43 and lightextracting film 34 in the vertical ZX meridian. In this form, +/−θ_(X)collimation 69 in the ZX meridian (pyramidal beam surface 70) is theresult of actions within light distributing optic 9, and +/−θ_(Y)collimation 71 in the vertical ZY meridian (pyramidal beam surface 72)is the result of the RAT reflector's pre-collimation +/−θ_(Y) (in air)initially in the horizontal ZY meridian.

FIG. 2B is a perspective view similar FIG. 2A, but illustrating themulti-segment capacity of this form of the present invention, in thiscase with four otherwise identical light distributing engines 1 of theform illustrated in FIG. 2A. The ability to assemble a contiguous, orsubstantially contiguous, array of parallel engine segments extends therange of output lumens significantly. About three light distributingengines of the geometrical dimensions illustrated in FIG. 2A can be usedto replace each light distributing engine of the square aperture formshown in FIGS. 1A-1D.

FIG. 2C is a perspective view illustrating the combination of seven (7)separate light distributing engine segments in the form shown in FIG.2A.

The multi-segment doubly-collimating engine variation illustrated inFIG. 2C shows no discrete, demarcation lines between its seven separateengine segments, either between the individual coupler elements (e.g.,individual etendue-preserving RAT reflectors) or between the sevencorresponding light distributing optic segments into which each RATreflector's output light is coupled. While each coupling optic 14 is asdiscretely separated from each other as the example in FIGS. 2A-2B, thesame degree of physical separation is not required for satisfactoryperformance of the corresponding light distributing optic 9. The generalqualities of the resulting doubly-collimated output illumination 10 aresubstantially equivalent whether seven individual light distributingoptic segments are used, as in FIG. 2B or whether a single segment madeto be the same size as covered by seven individual segments were usedinstead, as in FIG. 2C. The illumination system's far field output beam10 exhibits essentially identical angular widths +/−θ_(X) in meridian ZX(e.g. pyramidal surface 70) and +/−θ_(Y) in meridian ZY (e.g., pyramidalsurface 71),

Whether the resulting multi-segment light distributing engine 1incorporates an LED light emitter array of physically discrete segmentsas illustrated in FIG. 2B, or is fabricated as a single body made withindividual light transmission channels 68, as imagined in the example ofFIG. 2C, depends on manufacturing and packaging preferences.

FIG. 2D is a partially exploded perspective showing the seven-segmentLED light emitter array of FIG. 2C by itself at greater magnification.Element 74 is the first of 7 sequential coupling optic segments.Pyramidal solid 76 is a symbolic representation of the intermediatelypre-collimated output light generated by the collective output ofseven-segment LED light emitter 2, indicating its angular extent 78 inthe vertical ZX meridian as +/−φ_(X), and its more strongly-collimatedangular extent 80 in the horizontal XY meridian as +/−θ_(Y). As in theexamples above, a single beam representation is used for convenience,representing a continuum of illumination from the rectangular outputapertures of all seven RAT reflectors. The illustration (FIG. 2D) alsoshows an exploded (and magnified) view of illustrative LED emitter 3,which in this example has a square aperture bounding ring 82 thatsurrounds the emitters 4 separate chips 84, arranged internally in a 2×2array, and electronic substrate 86 (containing means for electricalinterconnections 88 and heat extraction).

The angle-spreading film sheets 52 and 54 introduced in FIG. 1D may beapplied with equal advantage to both the single segment andmulti-segment forms of the light distributing engines of FIGS. 2A-2D, aswill be shown in FIG. 2E.

FIG. 2E is a perspective view of FIG. 2D exploded just far enough toreveal the individual sections of input engine 60, while adding twoorthogonally-aligned angle-spreading sheets 52 and 54 (as in FIG. 1D).Such sheets are applied externally as illustrated just below lightdistributing optic 9 so as to modify (i.e., widen) the angular extents90 and 92 of the system's resulting far field output beam in one or bothmeridians. The unmodified narrower angular extents 70 and 72 are showndotted as a reference.

Practical operating applications of the thin doubly collimating lightdistributing engines 1 of the present invention, whether arranged in thesquare aperture form of FIGS. 1A-1D or the multi-segment form of FIGS.2A-2E, require structural chassis plates to hold and align theindividual constituents, including as well the associated powercontrolling electronic circuits interconnected with both an externalsupply of DC voltage and with the positive and negative electricalinterconnections 88 provided on each LED emitter 3 (as in FIG. 2D).Moreover, heat sink fins and heat spreading elements are required aswell for good practice of the present invention. While such system levellight distributing engine details have been introduced separately inU.S. Provisional Patent Application Ser. No. 61/104,606, representativeillustrations for each case will be provided further below.

Before doing so, the underlying details are described for preferredembodiments of each form of the present invention, with FIGS. 3-21,26-28, and 31-43 associated with the doubly-collimating square aperturelight distributing engine introduced generally by FIGS. 1A-1D, and withFIGS. 30A-30B associated with the doubly collimating multi-segment lightdistributing engine introduced generally in FIGS. 2A-2E.

FIG. 3A shows a perspective view of an example of a preferred embodimentof the present light distributing engine invention in its single-emittersquare output aperture form, generally shown in FIGS. 1A-1D. LED lightemitter 2 in this example comprises LED emitter 3 and anetendue-preserving RAT reflector form of coupling optic 14 as shown inFIGS. 1A-1D, but the generalized edge-emitting light guiding bar (orpipe) 18 is preferably formed by a tapered light guiding pipe 100 and aseparately facetted (micro-structured) light extraction film 102 that isoptically coupled in this example to the tapered backside edge of pipe100 by transparent coupling layer 106. The output edge of tapered lightguiding pipe 100 emits its pre-collimated output light across air gap 20into the input edge of light distributing optic 9, preferably a taperedlight guiding plate 112 having a separately facetted (micro-structured)light extraction film 114 (substantially the same micro-structure aslight extraction film 102) and optically coupled in this example to thetapered backside edge of plate 112 by transparent coupling layer 118(substantially the same as transparent coupling layer 106).

FIG. 3B is an exploded version of the elements shown in the perspectiveview of FIG. 3A that reveals previously hidden structural details.

FIG. 3C provides a magnified exploded view of the geometricalrelationships between LED emitter 3 (as illustrated in FIG. 2D),etendue-preserving RAT reflector 14 (in this example illustrated as ahollow 4-sided reflecting bin having symmetrically shaped reflectingsidewalls 131) and the corresponding input portion of tapered lightguiding pipe 100, including its square (or rectangular) input face 128(sized generally to match the D₁ by D₂ output aperture dimensions (133,135) of RAT reflector 14 as explained above).

FIG. 3D is a perspective view isolating on the relationship between thelight-cone 36 (as in FIG. 1C) output from illustrative RAT reflector 14,and its reduced-angle optical coupling to the dielectric medium of lightguiding pipe 100, shown as (dotted) cone 140. Light guiding pipe 100 ispreferably made of low optical loss sources of either poly methylmethacrylate (i.e., PMMA, acrylic) or polycarbonate. Generally, lowestloss is possible when using optical grade PMMA. When light guiding pipe100 has a 3 mm×3 mm square cross-section, and is made, for example, ofpolycarbonate, refractive index 1.59, preferable coupling performance isachieved, for example, when dotted light cone 140 is approximately inthe range of +/−30-degrees in both meridians (X and Z). This requiresthe angular extent of light cone 36 in air to be +/−Sin⁻¹ [1.59 Sin(30)]or +/−52.6-degrees in each meridian. Preferable coupling performance isachieved with a slightly wider angular range when using PMMA and itslower (1.49) refractive index.

FIG. 3E is a side view of the input elements isolated in FIG. 3D,showing the detailed angular distributions of the light as its conveyedfrom LED emitter 3, through illustratively hollow etendue-preserving RATreflector 14, and across a small air gap (exaggerated in scale forvisual convenience) into the initial region of light guiding pipe 100.Radiation pattern 142 corresponds to the light output from the outersurface of the LED chips of LED emitter 3, and from its nearly circularcross-section, indicating an almost perfect +/−90-degree Lambertianlight distribution. As this wide angular distribution passes throughillustrative RAT reflector 14 it is concentrated slightly in angularextent to one having in this example, +/−52.6-degree extent 144 in airby its etendue-preserving passage through RAT reflector 14. Then, oncecoupled into light guiding pipe 100, this light distribution compressesby Snell's Law to one having about a +/−30-degree extent 146 within thedielectric medium (taken as polycarbonate just for this example).

FIG. 4 is a top view of the complete doubly-collimating square aperturelight distributing engine system 1, as depicted in the perspective viewsof FIG. 3A-3B, showing the associated symmetry-driven geometricalrelationships in existence between the preferable LED light emitter 2, atapered light guiding pipe (or bar) 100 attached to facetted lightextraction film 102 and the preferable light distributing optic 9, atapered light guiding plate 112 attached to facetted light extractionfilm 114. Equation 1 relates the prevailing geometrical relationshipsbetween tapered light guiding pipe 100 thickness 150 (along X-axis 7)expressed as THKB, tapered light guiding pipe 100 length 152 (alongY-axis 5) expressed as LB, tapered light guiding plate 114 length 154(along X-axis 7) expressed as LP, the taper angle 156 of tapered lightguiding pipe 100 expressed as α_(b), the corresponding taper angle 157(not shown in FIG. 4) expressed as α_(p), the knife edge thickness 158of tapered light guiding pipe 100, and the corresponding knife edgethickness 159 (along Z-axis 6) expressed as KP (not shown in FIG. 4). Inthe present example for simplicity, α_(p)=α_(b) and THKB=THKP.

THKP=TKHB=(LP)Tan α_(p) +KP  (1)

FIG. 4 also shows a top view of the highly collimated edge-emitted lightdistribution 162 produced (generally directed along X-axis 7) and spreadover most of the output edge 126 (see FIG. 3B) of tapered light guidingpipe 100 within LED light emitter 2 as the light couples efficientlyacross air gap 20 into the body of tapered light guiding plate 112.Light distribution 162 is thereby representative of a continuum ofsubstantially equivalent light distributions 162 running parallel toeach other along edge plane 126 passing through points 159 and 161.

The core optical element utilized in this form of thin-profile lightdistributing engine 1 is the tapered light guide, whether deployed inits rod, bar, pipe or steeple-like form within LED light emitter 2 astapered light guiding pipe 100, or in its larger rectangular areatapered plate form as light guiding plate 112 as part of lightdistributing optic 9. The ability to collimate light in one meridian(and not the other) stems from the light spreading brought about bytotal internal reflections of light inside the tapered light guides(whether 100 or 112) combined with interactions between the guided lightand the facetted light extraction films (102 or 114) attached to (orplaced in optical proximity with) one of the tapered light guide faces(as shown in FIG. 3B). But the ability to collimate light in bothmeridians (e.g., producing the narrowly defined square and rectangularfar-field output beam profiles shown in FIGS. 1C, 1D, 2A, 2C, and 2E),stem from the sequential use of two tapered light guide-extraction filmcombinations, one for each orthogonal meridian. Substantiallyun-collimated light from LED emitter 3 is first pre-collimated in onemeridian by the first tapered light guide system (guide 100 plus film102). This processed light is received by the second tapered light guidesystem (guide 112 plus film 114), which collimates the light in thesubstantially un-collimated meridian, while transmitting light in thepre-collimated meridian without change. This two-step processing resultsin output light that's equally well collimated in both orthogonal outputmeridians.

In other words, the LED light emitter 2 within this form of lightdistributing engine collimates in one output meridian only, while thelight distributing optic 9 collimates in the other output meridian only,while simultaneously turning (or redirecting) the doubly-collimatedoutput light direction at some desired angle to the output aperture'ssurface normal.

The two communicating subsystems, LED light emitter 2 and lightdistributing optic 9 are separated from each other by a small air-gap20, with output edge 126 of one well-aligned with input edge 121 of theother.

Explicit examples are provided in FIGS. 5-20 below to explain (andprovide means for optimizing) the underlying physical mechanismsresponsible for the double collimation (and angular redirection)critical to this form of the present light distributing engineinvention.

As described above, the light emission from single LED emitter 3 (whichmay contain one or more individual LED chips) couples its emitted lightto input face 128 of tapered (dielectric) light guiding pipe (bar orrod) 100 by means of a coupling optic 14, that is preferably a square orrectangular (etendue-preserving) angle-transforming (RAT) reflector,whose four specularly reflecting sidewalls are mathematically shaped atevery point to reflect light at the proper angle to preserve etenduefrom the LED emitter's square or rectangular output aperture (as in 82of FIG. 2B) to the square or rectangular input face 128 of tapered lightguiding pipe 100 (according to the Sine Law cited above), whileconverting the LED emitter's near Lambertian input angles to an angularrange more suited to efficient light coupling to tapered light guidingpipe 100.

Tapered light guiding pipe 100 is made using a suitable molding processsuch as casting, injection, or compression-injection whose toolingenables formation of the flat plane mirror-quality edge surfacesillustrated, preferably using a transparent optical quality dielectricmaterial having an optical absorption coefficient in the visiblewavelength band that is as low as possible. Two suitable choices arepolycarbonate, refractive index 1.59 and polymethyl methacrylate (alsoreferred to as PMMA or acrylic), refractive index 1.49. Of these twolight guiding materials, PMMA is preferred for its lower level ofoptical loss. Arbitrarily, polycarbonate is used in the followingexamples.

More details on the pipe's tapered geometry are provided further below,but for the present example, the pipe's input face 128 is 3 mm×3 mm,it's effective taper length 154 (designated as α_(b) in FIG. 4) is 57mm, so that by geometry, its associated taper angle 156 (designated asα_(b) in FIG. 4), is α=Tan⁻¹(3/57)=3-degrees, independent of therefractive index of the material used. With an illustrative 3-degreetaper angle and 3 mm by 3 mm input face cross-section, light guidingpipe 100 draws down to knife-edge 158, which is preferably limited to a50 μm thickness or less, to maximize the effective output efficiency ofLED light emitter 2. (Light guiding pipe 100, as illustrated in theseexamples, begins with a linear extension 150 not counted in itsillustrative 57 mm effective taper length, as seen most clearly in FIG.4.)

Preferably, tapered light guiding plate 112 is sized to match (orsubstantially match) the rectangular geometry of the tapered portion oftapered light-guiding pipe 100. That is, edge face 126 of light guidingpipe 100 and corresponding edge face 121 of light guiding plate 112 aremade having substantially the same rectangular length and thickness soas to maximize their optical overlap and coupling efficiency. Theseconditions are generally satisfied when tapered light guiding plate 112has a cross-sectional thickness matching the corresponding thickness oftapered light guiding pipe 100 (i.e., in this case 3 mm), and whentapered light guiding plate is sized to match the effective length 154(designated LB in FIG. 4), making it in this case 57 mm by 57 mm. Thetaper planes (101 and 122) in both the tapered light guiding pipe (taperplane 101) and tapered light guiding plate (taper plane 122) of theexamples contained herein are oriented so their outside surfaces areeach facing in the opposite direction of the intended direction ofoutput light. The reverse orientations are also acceptable.

The two light extraction films (102 and 114) are formed preferably usingan optical material having the same or higher refractive index as thetapered light guiding pipe (or plate) they are being combined with. Thefacetted microstructures of the two light extraction films may beidentical, or made advantageously different (as will be illustrated inan example further below). In all ensuing examples, however, both lightextraction films (film 102 for pipe 100 and film 114 for plate 112) areillustrated as being laminated (i.e., optically coupled) to theirassociated taper plane (plane 101 for extraction film 102 and plane 112for film 114) preferably using an optical coupling layer (layer 106 forextraction film 102 and layer 118 for extraction film 114), the opticalcoupling layers having substantially lower refractive index than eithersurrounding extraction film, guiding pipe or guiding plate material.

One preferable material combination for light guides and extractionfilms within the present invention forms both light extraction films(102 and 114) and both light guides (light guiding pipe 100 and lightguiding plate 112) from polycarbonate, refractive index 1.59. For thiscombination to operate satisfactorily each light extraction film (film102 and film 114) is laminated to its light guiding counterpartpreferably using an optical coupling layer made of a PMMA orsilicone-based adhesive (i.e., layer 106 and layer 118) having arefractive index no greater than that of pure PMMA, 1.49, and preferablylower. The 0.1 refractive index difference between polycarbonate andpure PMMA facilitates light extraction in accordance with the presentinvention, as illustrated below. Adhesives Research manufactures a widerange of suitable optical coupling layer materials under their brandnames ARclad™ and ARclear™.

An equally preferable material combination for light guides andextraction films within the present invention forms both lightextraction films (102 and 114) and both light guides (light guiding pipe100 and light guiding plate 112) from PMMA, refractive index 1.49. Forthis combination to operate satisfactorily, however, each lightextraction film (film 102 and film 114) is laminated to its lightguiding counterpart preferably using an optical coupling layer made of alower refractive index PMMA-based or silicone-based adhesive (i.e.,layer 106 and layer 118). One preferable example of a preferablelow-index PMMA optical coupling layer is 50-μm thick ARclear™ 8932 withrefractive index 1.41. This choice of pressure sensitive laminatingadhesive is also manufactured by Adhesives Research and designated as anoptically clear silicone transfer adhesive having low haze and highclarity. The 0.08 refractive index difference between polycarbonate andstandard PMMA, and between standard PMMA and the low-index form of PMMA,equally facilitates light extraction in accordance with the presentinvention.

The tapered light guide (whether pipe 100 or plate 112) is an importantbuilding block of the present invention because along with the angularpreconditioning of input light preferably from LED emitter 3 provided bythe etendue-preserving RAT reflectors 14, the tapered light guideenables uniform output luminance to be achieved along its edge lengthfor the pipe and the length of its cross-sectional area for the plate,with approximately equal division of light between it's two planeboundary surfaces.

Although the general properties of tapered light guides have alreadybeen described and have been utilized in a few early fluorescentlighting applications, prior art descriptions are insufficientlyprepared for present purposes. No prior art teaching has everanticipated the deliberate combination of a tapered light guiding pipewith a tapered light guiding plate in a conjunctively orthogonal mannerthat provides well-collimated output light from the system in both itsoutput meridians (see FIGS. 1A-1D, 3A-3B and 4). Prior art teachinghasn't anticipated the unique angular input requirements that arise whencombining two tapered light guides according to the constraints ofequation 1 (see FIG. 4). Prior art examples haven't provided a suitablemeans for coupling wide emitting angle LEDs to tapered light guidingbars so as to output collimated light evenly and homogeneously along thebar's entire aperture length (see FIGS. 3C-3E and 5A-5C). And, prior artteaching hasn't anticipated the underlying relationships between inputcoupling conditions and the resulting near field spatial uniformity ofthe tapered light guide system that takes place in practicalembodiments, unique to such double-collimating illumination systems (seefor example FIGS. 48A-48C, 49, 50A-50H, 51A-51C, and 52).

For these reasons, we will first establish the underlying tapered lightguide behaviors pertinent to the present invention, and then we willintroduce the best mode embodiments.

All results provided herein, including the typical angular distributionsshown in FIGS. 1C and 3E above as initial examples, represent thoseobtained from realistic non-sequential optical ray-trace simulationsmade using the optical system modeling software called ASAP™ 2006,version 2, release 1 and ASAP™ 2008 version 1, release 1, manufacturedby the Breault Research Organization, Tucson, Ariz., which has beenarranged to allow correctly for multiple splits of the implicit Fresnelreflections that occur at all light guiding boundaries, with thedielectric media surrounding these boundaries, taken as air, (n_(MED)=1)as a typical example.

The schematic cross-section of the tapered light guide that underliesthe simulated behavior of both light guiding pipe 100 (Z-Y plane) andlight guiding plate 112 (Z-X plane) is given in FIG. 5A. Illustrativevalues are taken from the example described above. The prevailing taperangle 166, α=α_(p)=α_(b), is 3-degrees, taper length 168, L=LB=LP, is 57mm, light guide thickness 170, THK=THKP=THKB, is 3.037 mm, knife-edgethickness 172, K=KB=KP, is 50 μm, and the dielectric light guidematerial (medium), illustratively polycarbonate, has a refractive indexof 1.59. Comparable examples could be based on PMMA. The angularcross-section of simulated input light 144 (as in FIG. 3E) is applieduniformly over input face 128. When taper angle 166, knife edgethickness 172 and guide length 168 are fixed, the expression for guidethickness 170 follows from equation 1, THK=L Tan α+K. So, for theillustrative values, THK is geometrically, 3.037 mm (approximately 3mm).

FIG. 5A also shows the simulated (computer generated) output beams 180(upward taper side) and 182 (downward plane side), and their respectiveangular inclinations γ_(T) (upward taper side) and γ_(P) (downward planeside) 190 and 192 that arise from total internal reflection failures oflight rays transmitting within tapered light guide (whether 100 or 112)along both tapered mirror plane 184 (top side) and its flat mirror plane186 (bottom side). Topside output beam 180 is found to incline at abouta 16.5-degree angle 190 to the axis parallel to the guide's plan flatboundary plane 186, whereas bottom side output beam 182 is found toincline at a 19.5-degree angle 192 (for the illustrative case ofpolycarbonate, n=1.59). The approximately 3-degree difference betweenthese two results is due primarily to the tapered light guide's 3-degreetaper angle α, 166. The angular width (or extent) of each beam, FWHM, isabout +/−6-degrees. Approximately 50% of input light 144, in lumens, isfound within each far field output beam depicted. Changing the guidingmedium to a slightly lower refractive material such as equallypreferable PMMA (n=1.49) reduces each output beam angle only about1-degree, an has little effect on each beam's angular extent.

FIG. 5B shows three examples of the near field spatial non-uniformities(194, 196 and 199) that can result on tilted topside taper surface 184as a consequence of the angular extent of input light that is coupledinto entrance face 128 of the light guide cross-section of FIG. 5A.Spatial light profiles (194 and 196) arise on tilted top side tapersurface 184 for two illustratively different input light conditionswithin guide 100 or 112, one example being input light that transmitsinitially with a +/−52.6-degree cone (in air) in the plane of thecross-section (profile 194) and another example being light thattransmits initially with a narrower +/−38.97-degree cone (in air) in theplane of the cross-section (profile 196). The corresponding spatialprofiles (194 and 196) indicate the projected near field outputbrightness corresponding to any point along guide (bar or plate) length168 just outside the physical boundary of the illustrative polycarbonatemedia, n=1.59. Spatial profile 199 represents the behavior when inputlight begins with a widened +/−57-degree cone in air.

FIG. 5C shows the corresponding spatial light profiles (200 and 202)that arise on flat plane bottom side guide surface 186 for twoillustrative input light conditions within guide 100 or 112, lighttransmitting with a +/−52.6-degree cone in the plane of thecross-section (profile 200) and light transmitting with a+/−38.97-degree cone in the plane of the cross-section (profile 202).The corresponding spatial profiles indicate the projected near fieldoutput brightness corresponding to any point along guide (bar or plate)length 168 just outside the illustrative polycarbonate media, n=1.59.

Spatial light distributions (e.g., 194, 196, 199, 200, and 202) recordthe relative near field brightness uniformity of the illuminationprovided by the tapered light guide in the present example, and give atrue indication of the guide's aperture appearance when viewed directly(from above or below). The narrower the angular width (extent) of inputlight provided within the guide's cross-section, the more skewed is theappearance of its light output to the tapered (right hand) end of theplate, producing a dark zone (or band) closest to the source of lightinput. Conversely, input light cones wider than +/−53-degrees within theguide cross-section give rise to progressively more aggressive earlyemission and the corresponding appearance of a bright zone (or band) inthe vicinity of the guide's input face 128.

This more impulsive behavior is illustrated in FIG. 5B by profile 199for +/−57-degree input light (in air) to show one example of the strongeffect that can occur when the angular extent of the input light isimproperly arranged, for the guide's tilted topside plane 184. Eventhough the +/−57-degree input cone is only +/−4-degrees larger than the+/−53-degree cone giving rise to relatively uniform light distribution194, all the higher light angles extract immediately, and give rise to asizeable brightness peak. The wider the input angular cone, the moresevere the bright region becomes, and the darker the guide's tailsection output becomes. Despite such changes to near field apertureappearance, far field beam profiles 180 and 182 remain reasonablyunaffected.

Equally impulsive non-uniformity is observed for the more narrowlyconfined +/−38.97-degree input light, as revealed by spatial lightdistributions 196 (top side, FIG. 5B) and 202 (bottom side, FIG. 5C). Inboth cases, the more collimated input light within the guide delays theoccurrence of output and is associated with a visibly dark region in thevicinity of input face 128. Although the tapered guide eventuallyachieves a region of spatial brightness uniformity, this region onlyoccurs in the second ⅔rds of the guide length. The narrower the inputangular cone, the more extensive the input end dark region becomes.

The significance of the differences between spatial light distributions194, 196, 199, 200, and 202 as represented in FIGS. 5A-B is that theyreveal an important dependence between the uniformity of the lightguide's output brightness and the angular width of input coupled light.The best mode results, profiles 194 and 200 indicate that satisfactoryspatial uniformity is achieved over the entire guide length in thisparticular example when input light is held to an angular extent ofabout +/−53-degrees (in air, just outside the illustrative polycarbonatemedium).

It is impractical to derive an analytical equation for the input angularextent corresponding to widest output uniformity, as this result dependson the guide's specific boundary conditions and on the complex Fresnelreflections that arise because of them (and the refractive index of theguiding medium). The preferred optimization method for a differenttapered light guide structure is the stochastic, non-sequential opticalray trace performed noting the input angular extent that gives rise tothe widest and smoothest region of output uniformity that is possiblefor the prevailing materials and their geometric parameters.

Accordingly, best practice of the present invention arises when theangular extent of input light 146 coupled just inside the tapered lightguide's cross-section (as in the example of FIG. 3E) gives rise tosubstantially homogeneous near-field brightness uniformity illustratedby profiles 196 in FIG. 5N and profile 200 in FIG. 5C.

Far field output beams 180 and 182 are composed of the ensemble ofindividual light rays that have failed conditions for total internalreflection at the corresponding surface planes 184 or 186 within taperedlight guide. Total internal reflection behavior is illustrated morecompletely in FIGS. 6A-6B, for light guide sections taken relativelynear input face 128, and for ray trajectories at or near the prevailingcritical angle for the polycarbonate guide medium being illustrated.Similar behavior is illustrated when the guide medium is PMMA or anothersuitably transparent optical material.

The effects of adding a specular reflecting mirror plane (274 or 275)just beyond the tapered light guide's tapered boundary surface 184 orjust beyond the tapered light guide plane boundary surface 186 areillustrated in FIGS. 7A-7C and 8A-8D for the example of a polycarbonateguide medium and dielectric bounding layers existent between guide andmirror plane that are either air or PMMA.

FIG. 6A illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide.The ray path of single illustrative ray 206 from symbolic input source208 is traced from its point of entry just inside input face 128 of thelight guide's the refractive medium (i.e., polycarbonate, n=1.59, in thepresent example). Illustrative ray 206 strikes plane surface 186 atpoint 210, making critical angle 212 (θ_(c)=Sin⁻¹ [l/n]) with surfacenormal 214, which is 38.97-degrees for the polycarbonate light guidemedium of the present example. This ray 206 makes a total internalmirror reflection about surface normal 214 and is redirected towardspoint 216 on tilted plane surface 184 (tilted 3-degrees from horizontalin this example) as total internally reflected ray segment 218.Accordingly, the surface normal 220 at point 216 is tiltedcorrespondingly by 3-degrees with respect to plane surface normal 210,and because of this, ray 218 arrives 3-degrees short of the criticalangle 222. Since ray 218 arrives with an angle of incidence less thatthe critical angle, it refracts as output ray segment 224 into thedielectric medium (air in the present case) surrounding therepresentative light guiding cross-section according to Snell's Law. Ray218 is said to fail the condition for total internal reflection at point216, and as such refracting ray segment 224 is extracted as outputillumination within far field output beam 180 as was shown previously inFIG. 5A. This illustrative TIR failure is not 100% efficient because ofthe refractive index discontinuity that exists between the surroundingmedium air and polycarbonate in this example, which gives rise to aFresnel reflection at point 216 as reflected ray segment 226.

Fresnel reflections of this sort are conventionally calculated using theFresnel equations for reflection and transmission coefficients of theorthogonal (parallel and perpendicular) electric field components of anelectromagnetic wave, which are provided in most standard textbooks onelectromagnetic waves (for a more rigorous discussion, see for example,Jenkins and White, Fundamentals of Optics, 4E, McGraw-Hill, Section25.2.) In the present example, light is unpolarized, and ray tracesimulations assign proper light flux to each ray depending on itscomplex angular direction and the prevailing surface boundary conditionsaccording to an incoherent average of the two electromagneticpolarizations, as in equations 2 and 3, where θ_(i) and θ₁ are therespective angles of incidence and transmission with respect to theprevailing surface normal from Snell's Law. The closer the angle ofincidence becomes to the critical angle, θ_(c), at any surface boundarylike point 216 in FIG. 6A, the larger is the amount of light fluxcontained in the Fresnel reflected rays. If light flux in totalinternally reflected ray segment 218 of FIG. 5A is 1 lumen, about 0.815lumens are transmitted into air (81.5%) as ray 224 and 0.175 lumens arereflected at point 216 (17.5%) as ray 226. The splitting ratio betweentransmitted and reflected rays changes according to the angles ofincidence involved.

$\begin{matrix}{R_{AVE} = {0.5{( {\frac{{Tan}^{2}( {\theta_{i} - \theta_{t}} )}{{Tan}^{2}( {\theta_{i} + \theta_{t}} )} + \frac{{Sin}^{2}( {\theta_{i} - \theta_{t}} )}{{Sin}^{2}( {\theta_{i} + \theta_{t}} )}} )\lbrack {{Check}\mspace{14mu} {``A"}\mspace{14mu} {in}\mspace{14mu} R_{AVE}} \rbrack}}} & (2)\end{matrix}$

$\begin{matrix}{T_{AVE} = {0.5( {\frac{4\; {{Sin}^{2}( \theta_{t} )}{{Cos}^{2}( \theta_{i} )}}{{{Sin}^{2}( {\theta_{i} + \theta_{t}} )}{{Cos}^{2}( {\theta_{i} - \theta_{t}} )}} + \frac{4\; {{Sin}^{2}( \theta_{t} )}{{Cos}^{2}( \theta_{i} )}}{{Sin}^{2}( {\theta_{i} + \theta_{t}} )}} )}} & (3)\end{matrix}$

When Fresnel reflected ray segment 226 reaches point 230 in FIG. 6A, itsangle of incidence has moved further away from critical angle 212 as aresult of the reflection at tilted mirror plane 184. Its angle ofincidence with respect to dashed surface normal 214 is about 33-degrees,which is the critical angle, 38.97 in this case, minus two sequential3-degree angular reductions, one occurring on arrival at point 216 andthe second occurring on arrival at point 230. In this instance, theaverage transmission and reflection coefficients correspond totransmitted ray segment 232 contributing about 0.16 output lumens andFresnel reflected ray segment 234 containing about 0.02 lumens.Subsequent internal Fresnel reflections show diminishing contributionsas ray segment 238, 240 and 242 at points 236 and 242. The 1 lumen ofinitial light flux assumed in single illustrative probe ray 206contributes about 0.84 lumens (84%) to far field beam 180 and 0.16lumens (16%) to far field beam 182 in FIG. 5A.

The asymmetric flux splitting (as indicated by the net from an ensembleof the single-ray results illustrated in FIG. 6A) favoring contributionsto the upper far field beam 180 is significant only for this particulartype of single ray path, initially incident at (or near) point 214 andat incident angles at (or near) the critical angle for the guidingmedium used.

FIG. 6B illustrates the optical paths taken by a single paraxial testray undergoing total internal reflection inside a tapered light guide,choosing a slightly different start trajectory than the one shown inFIG. 6A. FIG. 6B traces the corresponding behavior of illustrative inputray 250, which arrives at point 214 with an angle of incidence 3-degreesgreater than illustrative ray 206. The internal transmission path of ray206 from FIG. 6A is shown as dotted for purposes of comparison.Accordingly, ray 250 in exceeding critical angle 212, makes a totalinternal reflection about surface normal 214 and is redirected towardstilted mirror plane 184 as ray segment 252, reaching it at shifted point254. Because the tilt of plane 184 in this example is 3-degrees and ray250 exceeded critical angle 212 by 3-degrees, ray 252 arrives at point254 with an incidence angle exactly equal to critical angle 212, andbecause of this, makes an efficient total internal reflection withessentially all its original flux remaining in reflected ray segment 256(i.e., no light transmission into the surrounding medium, illustrativelybeing air).

When ray 256 arrives at point 258, however, it has gained another3-degrees relative to the prevailing surface normal and as such falls3-degrees inside the critical angle. In this instance, the condition fortotal internal reflection is not satisfied, and refracted ray 260 istransmitted into the surrounding medium (air, in this example). As inthe case of ray 226 above, there is a Fresnel reflection at point 258,reflected ray segment 262 heading towards point 264 on surface 184.Arrival at point 264 also involves refractive transmission into thesurrounding medium as ray segment 266 and another Fresnel reflection,ray segment 268 along with transmitted component 272 at point 270.

Notice that in this example of FIG. 6B, despite being so close instarting trajectory to that in FIG. 6A, the majority of transmitted fluxis contained within output beam 260 (FIG. 6B) on the lower (or flatplane) side of light guiding cross-section. In fact, the output fluxcontributions (shown emboldened in both FIGS. 6A and 6B) are nearlyidentical, except for their side of escape. Other illustrative raytrajectory examples, if chosen, would be seen to cause a wide variety ofintermediary flux distributions between outputs from surface 184 and186.

When all rays within the angular extent of symbolic input light source208 are superimposed on each other, as in FIG. 5A, the average outputflux resulting on each side of bare light guide are contained in theequally energetic far field output beam profiles 180 and 182.

A specularly reflecting mirror-plane on one side of the tapered lightguide (or the other) is used to redirect light flux from one side of thelight guide to the other, so that effectively all extracted light ismade available through a solitary output aperture. The development ofthis basic behavior is illustrated by the same means in FIGS. 7A-7C.

FIG. 7A shows the effect on net output light extracted when adding atilted reflecting plane in air just above the tilted surface of thetapered light guide illustrated in FIG. 5A. When specular reflectingplane 274 (or 275) is placed near (or directly upon) either top orbottom surface 184 or 186 of the representative light guide (100 or112), the corresponding output light extracted from that light guidesurface is forced back into the guiding medium from whence it came by acombination of internal reflections and refractions, becoming a part ofthe collective output beam on the opposing side of the guide from thatof the reflecting plane's location. This behavior is illustrated by theside views of FIG. 7A (for tilted taper plane reflector 274) and 7B (forplane mirror reflector 275). The air-gaps between the light guide mediumand reflector 274 (FIG. 7A) and 275 (FIG. 7B) are 276 and 277respectively (but could in general be any transparent dielectric medium,preferentially having a lower refractive index than that of the guidemedium itself). In each case, the composite output beam (downward beamprofile 280, FIG. 7A, and upward beam profile 282, FIG. 7B) is directedaway from the horizontal X-Y plane illustrated by a wider angle, E, 284,than would be expected from either of the intrinsic output beam angles(γ_(T) 190 and γ_(P) 192) associated with the 2-sided-extractions ofFIG. 5A. Both single-sided beam extractions represented by realisticbeam profiles 280 and 282 are seen as being tilted by an additional8-degrees in the present example over the purely geometricalexpectation. Phantom two-sided beam profiles 180 and 182 representingthe far field beam profile results of FIG. 5A are included in dottedform for purposes of comparison. Phantom profiles 282 (FIG. 7A) and 284(FIG. 7B) are the mirror reflections of 180 and 182 respectively andeach is seen to differ from the actual double-sided beam profilephantoms by the taper angle α, which remains 3-degrees in the presentexample. Output beam 280 as shown in FIG. 7A projects downwards atapproximately a 27.5-degree angle, 286, measured from horizontal. Outputbeam 288 as shown in FIG. 7B projects upwards at approximately a24-degree angle, 290, also measured from horizontal. Correspondingangles from 2-sided extraction were about 19-degrees downwards and about16-degrees upwards (as determined in FIG. 5A).

FIG. 7C shows the effect on light extraction by adding a tiltedreflecting plane that is optically coupled to the tilted surface of thetapered light guide illustrated in FIG. 5A. Air gaps 276 (FIG. 7A) and276 (FIG. 7B) between reflector and light guide plate as used in lightdistributing engines 1 of the present invention are actually notnecessary to achieve best mode performance. Contrary to prior art,reflector 274 may be applied directly to surface 184 of therepresentative tapered light guides without significant compromise inefficiency (assuming reflectivity of the reflecting material issufficiently high). Reflector 274 is applied either by vapor deposition(as in the case of high reflectivity silver or aluminum) or as aseparate layer attached directly by means of a thin optical adhesivewhose refractive index nearly matches or is lower than the refractiveindex of the representative polycarbonate light guide material of thisexample. A direct reflector attachment method is used to advantage whenthe reflectivity of reflector 274 exceeds about 95%. One such excellenthigh-reflectivity reflector material available commercially for directattachment is ESR™ as supplied by Minnesota Mining & Manufacturing (3M).3M's so-called ESR™ mirror film material exhibits exceptionally highreflectivity (>0.98) for both polarizations of light over the entirevisible light spectrum regardless of angle of incidence. Elimination ofair-gap 276 in this manner sacrifices only a small amount of total lightoutput in beam profile 300. When ESR™ is separated from tapered lightguide surface 184 by a small air gap, about 95.8% of the input fluxresults in far field output beam 300. When ESR™ is optically coupled tothe plate, as with an index-matching pressure sensitive adhesive, outputconversion efficiency decreases only slightly to about 92%.

FIG. 8A-D shows perspective views of simulated performance for onepossible realistically constructed form of the tapered edge-emittinglight guide pipe invention introduced earlier. Far field light output inthis case, as anticipated by the mechanisms illustrated in FIGS. 5A-C,6A-B and 7A-B above, is well-collimated in one output meridian and notthe other as intended, while the output beam is directed obliquely fromthe light guide pipe's output aperture plane 126. In this elementalexample, plane reflector 274 is applied directly to tapered face 184 oflight guiding pipe 100. Light extracting and redirecting plane reflector274 is configured smoothly for purposes of this example, with lightextracting prisms 104 of light extracting film 102 as shown in FIGS.3A-B given peak angles approaching 180-degrees.

FIG. 8A is a perspective view illustrating the single LED light emitter2 serving as the input portion of the double collimating lightdistributing engine examples of FIGS. 3A-3B and 4, as seen from itsoutput edge 126, for the special case where its light extracting prismsfacets have collapsed to the unstructured form of a smooth mirror plane274. This LED light emitter example comprises single LED emitter 3, precollimating etendue-preserving RAT reflector 14 described above, andlight guiding pipe (bar or rod) 100. Illustrative light guiding pipe 100is made of polycarbonate, but could also be made of any other low-losstransparent optical material including PMMA, Zeonex, and non-absorptiveglasses such as quartz, Pyrex and Boro-silicates. Pipe 100 has a 3 mm×3mm input aperture, and a 57 mm taper length 168 (as in FIG. 5A). It'staper angle 156 as previously shown (e.g., see FIG. 4), is preferablyabout 3-degrees. The pipe's top and bottom planes 184 and 186 are flatand parallel. The 3-degree taper is cutoff with a 50-μm thick knife-edge158. The RAT reflector's input aperture is sized to match the emissionaperture of LED emitter 3, which is sized 2.4 mm by 2.4 mm so as toreceive substantially all the light from a 2×2 array of 1 mm by 1 mm LEDchips. Two of many possible commercially available 4-chip LED emittersmeeting this particular illustrative condition include variousconfigurations of LED emitters manufactured by Osram Opto Semiconductorunder trade names OSTAR™ Lighting and Osram OSTAR™ Projection. The RATreflector's corresponding output aperture is made 3 mm×3 mm, so as tomatch the light guide pipe's 3 mm×3 mm input aperture, while alsosupplying the approximately the +/−52.6-degree angular distribution (inair) associated with the preferable results of FIG. 5A-5B.

FIG. 8B provides a topside view of the edge-emitting LED light emitter 2of FIG. 8A, showing the obliquely directed far field beam cross-sectionthat results. The actual computer-simulated far field output beam 310for the example conditions is superimposed accurately in cross-section,and found to make in air a 27-degree angle 312 (as shown) with the lightguiding pipe's output aperture plane 126. This far-field beam'scross-section has about a +/−8-degree angular extent, FWHM (e.g., fullwidth half maximum).

FIG. 8C provides a front view illustrating the light beam cross-sectionthat is emitted from the output edge of the system of FIG. 8B. Thecomputer-simulated far field beam 310 is superimposed accurately in thisdifferent cross-section, and found to make in air the unmodified53-degree out angle 316 that was established by design at the pipe'sinput by RAT reflector 14.

FIG. 8D illustrates the LED light emitter of FIGS. 8A-8C in a topsideperspective view showing the highly asymmetric nature of its obliquelydirected output illumination. As in FIGS. 8B-8C, far field beam profile310 as illustrated was obtained by computer simulation and issuperimposed in its corresponding perspective as emanating from outputedge 126 of light guiding pipe 100 within LED light emitter 2.

Extending the light extraction behavior of the present invention to thesteeper output angles better suited to down lighting requires anadditional light processing mechanism within the tapered light guide'sunderlying extraction mechanism.

FIG. 9 illustrates the side cross-section of a tapered light guidingpipe 100 (or plate 112) whose tilted (taper) plane 184 is modified toinclude an optical film stack 321 having two different dielectric layers(320 and 322) and a plane mirror 274, with a superimposed simulation ofthe extracted output light's angular cross section. The addition ofoptical film stack 321 introduces an initial step in this importantmechanistic variation for the tapered light guide configuration asillustrated schematically in FIG. 7A. This modification applies equallywhether the tapered light guiding member is a pipe 100 or a plate 112,and whether the guiding material is polycarbonate (as in the ongoingexample, PMMA, or some other more preferable optical material such asPMMA having higher transparency). It further applies whether the lightguiding plate has been extruded linearly, as in the present example, orextruded radially, as discussed further below (e.g., see FIGS. 34A-34F,35A, 38A-38B, and 39A-39C). The side cross-sectional view of FIG. 9shows two thin optically transparent dielectric layers substituted forthe air-gap 276 as shown in FIG. 7A. The first of these layers, layer320, is chosen to have a lower refractive index than that of thematerial used to form the light guiding pipe or plate to which it iscoupled. In the example of FIG. 9, the light guide material is takenillustratively as being polycarbonate, n=1.59, and the refractive layer320 which is attached to tilted boundary plane 184, has a refractiveindex preferably less than 1.49. Were the light guide material made ofacrylic (poly methyl methacrylate), n=1.49, the refractive layer 320which is attached to tilted boundary plane 184, has a refractive indexpreferably less than 1.41. The second of these layers, layer 322,attached to the first, preferably has a refractive index equal to orhigher than that of the refractive index of the light guiding member(100 or 112) When the light guide is polycarbonate, layer 322 preferablyhas a refractive index greater than or equal to 1.59, and when the lightguide layer is acrylic, layer 322 preferably has a refractive indexgreater than or equal to 1.49. Reflector plane 274 is applied directlyfor this example to the upper surface of layer 322. Layer 320 may be anyoptically transparent material having a refractive index between about1.35 and 1.55, whose thickness is preferably less than 100 μm, but mayrange upwards from as little as about 50 μm. In practice, layer 320 ispreferably made of an adhesive material formulated from acrylic (polymethyl methacrylate), refractive index between 1.47 and 1.49 when thelight guide is made of polycarbonate and between 1.39 and 1.41 when thelight guide is made of pure acrylic (e.g., see Adhesives Research Inc,Philadelphia, Pa.). Layer 322 is preferably made of the same material aslight guide (100 or 112) in practice, but may also be any polymeric orglass material with equal or greater refractive index than that of thelight guide. The thickness of layer 322 is preferably less than 250 μm,but may range upwards from about 50 μm to thousands of microns and moredepending on the intended purpose. FIG. 9 also shows, in cross-sectionalview, one possible far field beam simulation 318 that results fromtransmission of input light 208 through the tapered light guide (100 or112) right up to reflector plane 274, and just inside the dielectricmedium of layer 320.

FIG. 10, is based on a set of computer ray-trace simulations, and plotsout the quantitative relationship existing between the refractive indexchosen for transparent dielectric layer 320 and the internal far fieldbeam angle that results in transparent dielectric layer 322 just beforeplane reflector 274. The internal angle produced using acrylic as layer320 is 24-degrees away from output aperture plane 186. More ideal beamshape is associated with a refractive index value closer to 1.35, whichproduces a far field angle of 33-degrees. The results of FIG. 10 applyto the example using a polycarbonate light guide. A similar trend isobserved when the light guide is made of a lower index material such asacrylic.

The relationship between capture angle and the refractive index ofmedium 320 that is set forth in FIG. 10 indicates that the lower therefractive index of medium 320, the cleaner and narrow is extractedlight beam 318, and the greater is its angle with horizontal. Thesmaller the refractive index difference between tapered light guide pipe(100) or plate (112) and medium 320, the shallower the extraction angleand the more distorted is the extracted beam profile.

Turning the refracted light in layer 322 into a steeper angle thanprovided by its Law of Reflection angle from tilted plane mirror 274requires installing an even steeper mirror angle than that of the lightguide's natural 3-degree taper angle. Rather than doing this by simplyincreasing the steepness of tilt for the entire reflector plane 274 from3-degrees to an angle as high as about 40-degrees, it is preferable toFresnelize the steeper mirror as a sequence of substantially identicalreflecting facets, as anticipated earlier by light extraction films 102shown in FIGS. 3A-B and 4 above. The process of Frenelizing a thickspherical or cylindrical optical surface shape is standard practice inthe optics industry as a practical means of reducing an opticalelement's net thickness (e.g., the field of Fresnel lenses). Its usageis equally appropriate in reducing the thickness of an otherwise steepplane mirror surface. Such is the case with the light reflecting facetsthat are applied in the present invention to achieve more desirableoutput angles in conjunction with the tapered light guiding pipe 100 andthe tapered light guiding plate 112, and their conjunctive applications.

The basic light extraction mechanism involved, whether applied to thetapered light guide pipe (100) or plate (112) is illustrated by way ofthe cross-sectional view provided in FIG. 11A and the magnifiedcross-sectional view of FIG. 11B for material and geometric values ofthe ongoing example. In this example, both the tapered light guide andfaceted dielectric layer 322 are made of polycarbonate, refractive index1.59, and dielectric coupling layer 320 is made of an optically clearacrylic adhesive, refractive index 1.49. Left side apex facet angle,β_(L), 350 and right side apex facet angle β_(R), 352, are illustratedin the magnified detail of FIG. 11B. They are respectively, 38-degreesand 60-degrees in the present example, but many other suitableillustrative combinations will be established. The array offacetted-prisms is a regular one in this example, but a wider variety ofprism compositions may be blended into a more complex array for specialapplications. And while the basic light extraction mechanisms apply tolight guiding pipes 100 and light guiding plates 112, they apply equallywell to light guiding disks formed by rotating the tapered cross-sectionof FIG. 11A about an axis parallel to input face 128.

FIG. 11A shows the underlying behavior by tracing the path of oneillustrative light guiding probe ray 330 (plus sequential segments 332,334 and 336), and also by showing the resulting redirection of thecollective far field output beam 336 representing an ensemble of alloutput rays.

Full extraction of internal beam 330 from generically tapered lightguide pipe (100) or plate (112) while simultaneously changing beamdirection to a more preferable one for the present invention is achievedin cross-sectional view with facetted redirection layer 102 which iscomposed of a sequential series of left hand and right hand reflectivefacets (340 and 342) made in layer 322 placed just above lower indexlayer 320, as shown in the side view of FIG. 11A. The asymmetric facets340 and 342 are formed, for example, in a clear polymeric medium such aspolycarbonate, and surface-coated with metallically reflective,pinhole-free film, preferably silver, which also could be aluminum oranother high-reflectivity coating.

By this design, light extraction in the present invention occurspredominately, if not exclusively, on right hand facets 342 in thisarrangement. Extractable rays such as 4240 in tapered light guide 4100pass through low index layer 4212 (ray segment 4242) and then throughfacetted medium 4236 (ray segment 4244) along the direction of extractedbeam 4210 in FIG. 41A. Redirection occurs by reflection at the tilt ofright hand facets 4234, as illustrated for one facet in FIG. 42A.Redirected beam 4246 contains ray segment 4248 along with all otherredirected rays surrounding it.

FIG. 11B provides a magnified view 329 of the asymmetric facet geometryapplied in this illustrative example. The total included apex angle 352(β_(T)) is the sum of left hand facet angle 354 (β_(L)) and right handfacet angle 356 (β_(R)), each defined with respect to surface normal 351for the interface 358 between film layer 322 and lower index layer 320.When output light is preferably directed normal to the associatedtapered light guide's output face (126 for pipe 100 and 123 for plate112), the total included apex angle 352 is about 98-degrees, left handfacet angle 354 is about 38-degrees and right hand facet angle 356 isabout 60-degrees, as mentioned above for values used in the ongoing. Thefacet depth 360 (FD), along with the respective facet angles determinesprism pitch, which is by geometry, FD [Tan (β_(L))+Tan(β_(R))], where FD[Tan(β_(L))] is sub-length 370 and where FD [Tan(β_(L))] is sub-length372. Redirection of extracted light is controlled predominately (if notexclusively) by the right hand facet angle 342.

FIG. 11C supports this description by showing the correspondingcross-sectional side view of a ray-trace simulation of 500,000 inputrays 208 for this illustrative configuration, plotting every 1000^(th)ray for viewing simplicity. It's easy to see from this presentation thatthe array of right hand facets (342) serve as the source ofdown-directed illumination, while the left hand facets appear only asintervening dark stripes. With these introductory elements as afoundation, some illustrative examples will be given of practicalembodiments of the present invention.

The first example will provide additional performance details of thesingle LED form of tapered edge-emitting light bar input engine 120introduced earlier in FIGS. 3A-E and 4, using facetted multi-layeredlight extraction film 102.

FIG. 12A provides another exploded view of the tapered edge-emittinglight bar input engine 120 clearly showing the construction of itsmulti-layer light extracting, turning and collimating film 102.

FIG. 12B shows a top view of input engine system 120 including its farfield output beam pattern, a +/−6-degree collimated beam 162 that'sextracted into air. Also shown is the internally pointing far field beamcross section just inside output aperture 126 of tapered light guidingpipe 100, +/−3.77-degree collimated beam 380. Using the values of theongoing example, as provided above, the output beam from this engine isdirected along the system's X-axis 7. As will be shown further below,different facet angle combinations may yield a wide variety of outputpointing directions other than the axial one.

FIG. 12C shows the information contained in FIG. 12B, but in aperspective view that shows the Z-meridian angular extent 384 of farfield output beam 162, as well as the high degree of comparativeY-meridian angular collimation 386.

FIGS. 12D and 12E are both perspective views of input engine 120 thatshow the near field spatial uniformities 390 and 392 resulting from twodifferent coarsenesses of prism period for prismatic light extractionfilm 102. The finer (smaller) the prism pitch, the finer is theresulting near field brightness non-uniformity.

FIGS. 12F-H explore this trend clearly from the distinct black and whitebars of the 57 mm long edge uniformity pattern 390, to the smaller barsin pattern 392, and then to the practically indistinguishable bars ofpattern 396, which represents 160 μm prism periods.

FIGS. 13A-C emphasize the relationship, discussed preliminarily above,existent between the input angular distribution (400, 402 and 404)provided in the X-meridian by RAT reflector 14 coupling LED input lightto input aperture 128 of the tapered light guiding pipe 100, and thenear field spatial uniformity pattern resulting along the tapered pipe's57 mm output length (410, 412, and 414). These results use the 160-1 μmperiod form of prismatic light extraction film 104, isolated as 406.

Input angular distributions 400, 402 and 404 in air prior to couplingacross input aperture 128 are shown separately as FIGS. 14A, 14C and14D, and are approximately +/−33.6-degrees, +/−52.6-degrees and+/−65.0-degrees respectively. The input angular extent that is shown inFIG. 14B is approximately +/−41-degrees. It's easy to see that the bestnear field uniformity is achieved in FIG. 13B, as a result of+/−52.6-degree input light distribution 402.

FIG. 15 is a graphical representation of the engine systems fourillustrative near field spatial uniformity profiles, 410, 412, 141, and416 as a function of the four angular distributions, 400, 401, 402 and404 shown in FIGS. 14A-D. The angular distribution patterns responsiblefor the four illustrative near field spatial uniformity profiles aresuperimposed on FIG. 15 emboldened and underlined as 400, 401, 402, and404.

The second example, FIGS. 16A-16B, shows the conjunctive far fieldillumination patterns that result when tapered edge-emitting inputengine 120 is combined with tapered light guiding plate 112, as shownearlier in FIGS. 3A3E and FIG. 4, but with the finer pitch (period)prismatic light extraction film shown above. The distance between thisthin-profile illumination system 1 and the 1800 mm×1800 mm far-fieldsurface illuminated is 1500 mm.

FIG. 16A shows a perspective view of the geometry involved, includingthe computer simulated far field beam pattern that results. Theillustrative 57 mm×57 mm×3 mm dimensions of illumination system 1, thecomplete system noted as 430 in this example, is rendered exactly toscale with respect of the 1800 mm×1800 mm length 436 and width 438 ofthe surface 440 to be illuminated from a height 442 that's 1500 mm away.

FIG. 16B provides magnified view 444 of the thin-profile doublycollimating illumination system noted at 430 in FIG. 16A.

FIG. 17 is a computer simulated 2D graphic representation of the farfield illumination pattern 450 made on far field surface 440 asilluminated in the perspective view of FIG. 16A. The angular extent ofbeam pattern 450 in this example is approximately between +/−5-degreesand +/−6-degrees full width half maximum (FWHM) in both meridians shown(X meridian along length 436 and Y meridian along width 438. The linewidth profiles in each meridian are shown as the set 452 and the singleprofile 454. White arrow 451 denotes the X meridian line width profilecorresponding to the pattern shown, 450. The other X meridian line widthprofiles correspond to additional simulation runs with different valuesof right hand facet angle 352 (see FIG. 11B). A slight change in the farfield angular pointing direction results from slight changes in thenominally 60-degree apex angle, α_(R).

FIG. 18 is a graphic representation of a set of differently tilted farfield beam cross-sections generated by the illumination system of FIG.16A in response to five slightly different choices of facet angleswithin the prisms applied to the surface of its tapered light guidingplate.

This facet-angle means of controlling the illumination system pointingdirection is a very powerful feature of the present invention. Flatmounted illumination systems 430 of the present invention can bedeployed to provide obliquely pointing illuminating beams and far fieldpatterns with the degree of beam pointing obliqueness set by choosingthe extracting film's prismatic facet angles appropriately.

The spatial overlap of the five far field beams caused by a distributionof the same five choices of facet angles within a single 57 mm×57 mmlight extraction film may be applied to tapered light guiding plate 112,resulting in uniformly widened far field beam profile. For smoother(less discrete) beam distributions, a greater number of facet-anglechoices may be included.

FIG. 19 is a graphic representation showing nine different far fieldbeam cross-sections to demonstrate the +60-degree to −60-degree range ofbeam directions that are accessible by means of varying internal lightredirecting prism angles within the thin-profile light guidingillumination system's light distributing plate 112. FIG. 19 shows thepower of this means of facet-angle tailored angle spreading within thepresent invention for the nine widely different far field beamdirections (500, 502, 504, 506, 508, 510, 512, 514, and 516) eachcreated in the X meridian about system surface normal 441 by merelychanging the right hand facet angles (□_(R)) in the 57 mm×57 mm lightextraction film 480 of the present example as referenced by thearrangement shown in the perspective view of FIG. 16B.

FIG. 20 contains a graph of prismatic facet angles within lightextraction and turning film versus the far field beam-point angle itcreates, for the thin-profile light guiding illumination system of FIG.3A. While the functional relationship expressed in FIG. 20 is for thepolycarbonate light guiding plate 112 of the present example, a similarfunctional relationship exists for other material combinations such theone associated with an acrylic light guiding plate 112. FIG. 20 revealsthe underlying physical relationship existent between the right handfacet-angle, in degrees from apex normal 441 as discussed earlier, andthe far field beam pointing angle measured from the normal to thesystem's output aperture plane. It is seen that by this method, beampointing may be varied over the full angular range from −60-degrees to+60-degrees. The dotted line in FIG. 20 is a linear fit to the simulateddata and has an intercept value, b=59.5 and a slope value, m=0.309, inthe equation α_(R)=mφ_(P)+b, with φ_(P) being the pointing angle indegrees measured from the system's surface normal.

The far field illumination pattern's angular diversity is expandedwithin the present invention in several other ways, applied separatelyor in combination. A first means of output angle control, mentionedearlier with regard to the embodiment of FIG. 1D, involves use of one ortwo output light conditioning layers 52 and 54 in the form of alenticular type of angle-spreading diffusers. The second means of outputangle control involves use of collimated edge light sources whose degreeof input collimation may be adjusted in a way that alters the angularextent of far field illumination (as described above as in FIGS. 2A-2C.The third means of output angle control involves the variation on thedistribution of prism facet structures within the light extractingredirection layer as shown just above.

Of these approaches for widening the illumination system's angularextent beyond the nominally +/−5-degrees illustrated above, adding oneor two angle-spreading diffuser sheets (preferably lenticular anglespreading sheets 52 and 54) across system's square or rectangular outputaperture (e.g., as illustrated earlier in FIGS. 1D, 2D and 4) may be themost easily applied. As reasonably well-collimated light beams of theinstant invention pass through any one or two-dimensional anglespreading diffusing sheet their beam profile is broadened by the anglespreading mechanism involved. Substituting one set of light spreadingfilms for another makes the desired changes to the light engine's outputlight distribution.

Several prior art light diffusing sheets may be used in this mannerwithin the present invention, including bulk scattering-type diffusers,spherical lenticular type lens sheets, and various diffractive typelight shaping diffuser sheets. Yet one particular variation of lightingspreading diffuser sheet, a lenticular lens sheet with parabolic lenselements, will be shown as having unique attributes that are preferablefor uses of the present invention.

FIG. 21 is a side cross-section illustrating the computer ray-tracesimulated far field angle spreading behavior of a prior art form of bulkscattering-type diffusing sheet applied in the output aperture of thethin-profile light guiding illumination system of FIG. 3A. FIG. 21superimposes a family of typical diffusively broadened far field beamprofiles 520, shown for visual convenience as being normalized withrespect to their on axis intensity. Each profile actually distributesapproximately the same number of output lumens to field surface 522.Silhouette 524 (shown in black) represents the far field beam profile ofthin-profile illumination system 1 of the present invention without anyexternal light spreading diffusion. Far field beam profiles 526, 538,530 and 532 are illustrative of the type of beam spreading that ispossible, 526 (+/−10-degrees), 528 (+/−15-degrees), 530 (+/−25-degrees)and 532 (+/−30-degrees). In addition to widening the light emittingengine's angular extent, diffuser 534 also hides a wide variety ofinhomogeneities in brightness uniformity caused by manufacturing defectsor tolerance violations. A system height 540 of 1500 mm was taken forthis comparison.

Luminit LLC of Torrance, Calif. (formerly Physical Optics Corporation)manufactures one line of diffractive light diffusing sheets made forthis purpose. Their commercial light-shaping diffusers scattercollimated input light (by means of holographic diffraction)predominately in the forward direction, with a wide range of selectableangular cones (e.g., +/−10-degrees, +/−15-degrees, +/−20-degrees,+/−30-degrees and +/−40-degrees in circularly symmetric cones, and+/−5-degrees by +115-degrees, +/−5-degrees by +/−20-degrees,+/−5-degrees by +/−30-degrees, +/−17.5-degrees by +/−37.5-degrees,+/−17.5-degrees by +/−47.5-degrees and +/−30-degrees by +/−47.5 inasymmetric cones).

Other conventional diffuser sheets 534 that can be used in this samemanner within the present invention include, whether individually or incombination, adhesive resins or polymer sheets loaded with scatteringpowders such as for example titanium dioxide or fluorescent oxides,clear plates coated with opalescent or fluorescent material, androughened sand blasted glass or plastic plates.

Another way of widening the nominally +/−5-degree angular extent outputfrom light engines of the present invention is by adding one or twospherical lenticular lens sheets across the light emitting engine'soutput aperture. Lenticular lens sheets are thin transparent elementsformed by a linear array of nominally identical lenses. Lenticularlenses in the prior art are most commonly spherical ones, but have alsobeen prismatic. For example, see the schematic cross-sectional side viewin FIG. 22A and the perspective view of FIG. 22B.

Other prior art light spreading diffuser examples have includedtwo-dimensional arrays of micro lenses and two-dimensional arrays ofpyramidal cones. Most of the associated prior art teaching has beenconcerned with using such micro lens sheets for near field lightdiffusing applications such as homogenizing and expanding the angularcone of the general back illumination provided by so-called backlightsto the rear side of directly viewed liquid crystal display (LCD)screens, as in cell phone displays, laptop computer displays and desktop monitor displays.

One company, RPC Photonics of Rochester, N.Y., however, produces a lineof Engineered Diffusers™ using various mathematically developedtwo-dimensional distributions of micro-sized lenslets of considerableshape diversity (see topographic schematic representation of a typicalsurface region for this type of diffuser in FIG. 22C). In this specialcase, the clear optical lens sheet material has a pebbled morphologycomposed of nominally 1-100 μm sized lens elements varying from thesteeper-walled cone-like shapes 600, and spherical shapes 602, to evendistorted spheroids 604 and 606. Tooling masters for such complexmicrostructures are laser written in photo-resist and then delineatedphotolithographically. Commercial RPC Photonics products are made bycasting and curing, by compression molding and by injection molding.Such distributed lens light shaping diffuser products could be designedfor effective use as an angle spreading diffuser sheet 534 within thepresent invention. The pebble-lens Engineered Diffuser™ approachprovides convenient means to realize a much wider range of far fieldlight distributions from the well-collimated light-emitting engine thanwith any other prior art lenticular type micro lens sheet approach.

While this method may be applied to light emitting engines of thepresent invention, a simple variation of the lenticular-type anglespreading lens sheet has been found that is less costly to fabricate andhas a an equally customizable light-spreading performance.

Since the doubly collimated far field output beams from illuminationsystems 1 of the present invention are intrinsically well collimated intwo orthogonal meridians, there is no immediately pressing need for thecircularly symmetric lens elements developed by the method of FIG. 22C.While some applications may benefit from the implied randomness of pitchin this approach, the simpler stripe-like lens elements of a lenticularsheet, with stripe axes made orthogonal to the plane or planes ofcollimation, may be quite sufficient for the various best mode lightdistributions needed in down and wall lighting applications of thepresent invention.

Manufacturing processes for lenticular lens sheets are readily availableand offer lowest possible manufacturing costs. Lenticular sheets can beformed by low-cost plastic extrusion because of their longitudinallygrooved nature. In addition, 3M's prolific brightness enhancing filmproducts (e.g., BEF-T™) are lenticular structures of nominally 50-μmwide Porro prism grooves with internal prism angles being 45-degrees,90-degrees and 45-degrees. Such prism sheets are routinely manufacturedtoday by high volume roll-to-roll acrylate-based casting and curingprocesses in very high volumes with intrinsically low manufacturing cost(per square foot). The same materials are also readily manufactured byhot embossing. Manufacturing qualities of these effectively embossedmicrostructures are best when the lenticular grooves run down the lengthof the processed rolls of the continuously replicated material. Microreplication of features having complex shape variations running acrossthe roll as well as down its length (e.g., those of the pebble lenses ofFIG. 22C) is feasible, but more difficult to produce on a reliablebasis. Pebble-type lenses are incompatible with extrusion.

FIG. 22A represents a schematic cross-sectional side view of a prior artform of a cylindrical lens array film containing spherically shaped lenselements known as a lenticular diffuser or lenticular diffuser sheet.The traditional prior art lenticular diffuser sheet, illustrated byschematic cross-section in FIG. 22A, is an optically transparent film orsheet material 550 made of a polymer or glass composition whose planesurface 552 is formed to contain a micro structured array 554 ofparallel lens cross-sections, each lens cross-section (sometimes calleda lenticule or a lenticular) having generally identical cross-sectionalshape 556, SAG 558 and a corresponding pitch or repeat-period PER 560.When the individual lens cross-sections 562 are concave or convexportions of a spherical (or aspheric) cylinder lens, the SAG and the PERare related by simple geometrical expression given in equation 4-7,equation 6 representing the SAG for classical spherical curvature, andequation 7 representing the SAG for a classical aspheric curvature(including all possible polynomial shapes, comprising ellipses,parabolas, hyperbolas, and conic sections). In most cases SD=PER/2, andspecifies one half of the lens period PER, RLEN representing theassociated radius of curvature, CC representing the conic constant(traditionally −1 for parabolic curve, 0 for a sphere, >1 for ellipticalcurve, and >1 for hyperbolic curves), and A1L, B1L, C1L and D1Lrepresenting the first through fourth aspheric coefficients.

KK1L=(SD)²/ABS(RLEN)  (4)

KK2L=((SD)/ABS(RLEN))²  (5)

S00=KK1L/[1+SQRT(1−(1+CC)(KK2L))]  (6)

SST=S00+(A1L(SD ⁴))+(B1L(SD ⁶))+(C1L(SD ⁸))+(D1L(SD ¹⁰))  (7)

FIG. 22A shows that ideal illustrative collimated rays 564 or 566 passthrough diffuser sheet 568 parallel to surface normal 580 and arerefracted by the optical power of the individual lens elements 556 inthe array 554 through the corresponding focal points 570 or 572. Theserefracted light rays then diverge with increased angular extent 574 or576 that, to only rough paraxial approximation, is a predictablefunction of the lens's characteristic focal length. Paraxialapproximations are unreliable because they represent a very smallfraction of the total volume of realistic rays involved, because totalinternal reflections may occur within the sheet, and because estimationsof the collective skew ray transmissions through an asperhically shapedelement is extremely challenging, and is generally only addressed bycomputer based ray tracing.

In addition to this, the prior art stands notably silent on thepractical distinctions between far-field illuminating results associatedwith collimated rays first striking the plane surface 574 of lenticularlens sheet 568 and those first striking the curved lens surfaces 562.While both orientations produce useful results for some illuminationapplications, the results are in fact strikingly different in quite afew cases, not only in effective transmission efficiency, but also inthe far-field light distributions themselves. And, these differenceswill be shown of significant value when practicing the presentinvention.

Commercially available lenticular lens sheets are primarily spherical intheir lens cross-sections and made for use as near field 3D imaging lensoverlays on top of suitable images (sized from inches on a side to manyfeet on a side). They also are used for decorative visual effects on awide variety of packages. One typical manufacturer of lenticular sheetsis PACUR of Oshkosh, Wis. Their lenticular sheet products are made byembossing polyester resin with 40-100 lens elements per inch,corresponding to lenticular widths of PER=0.251 mm to PER=0.635 mm, andlenticular radii of 0.251 mm to 0.371 mm. Lenticular sheets are alsomade of acrylic and polycarbonate. Other manufacturers include forexample, Human Eyes Technologies Ltd. Jerusalem, Israel, Micro LensTechnology (Indian Trails, N.C.). In imaging applications of lenticularlens sheets, the planeside 574 of the lenticular sheet 568 is laminatedonto the image layer and reflected light passes outwards through thelenses towards the viewer. The imaging (or viewing) properties oflenticular products cannot be used to predict the effects on far fieldillumination.

Reliable descriptions of a lenticular diffuser's actual angle wideningeffects on far field illumination, even those commercially available forother applications, are only possible by direct experiment and, as inthe present example, by lab validated computer simulation. When properlyimplemented, computer simulations of a lenticular lens sheet's opticalperformance duplicate the results of reference laboratory experiments,and enable discovery of new and useful lenticular implementations.

As an example of a spherical lenticular prior art example that doesagree with paraxial theory, we present the far field illuminationperformance of one of the lenticular products with used in commercial 3Dimaging: PACUR's LENSTAR 3D. It has 100 lenticulars per inch, alenticule radius 4527 of 0.0092″ (0.23368 mm) and a lenticule width(PER) 4512 of 0.0101″ (0.25654 mm). The associated SAG 558 is 0.3835 mm,and the implied focal length (572 in FIG. 22A) is 0.5842 mm. This focallength predicts a far field illumination cone by the thin lens paraxialapproximation of +/−12-degrees (24-degrees full angle). PACUR reports a30-degree field of view in imaging mode applications.

FIG. 23A and FIG. 23B show the far field behavior for collimated+/−5-degree input light provided by doubly collimating light emittingsystem 1 as described earlier, or any other similarly collimated lightsource. FIG. 23A shows the result when the lenticulars point away frominput light 650, and FIG. 23B shows in this case the very similarresults when the lenticular vertices point towards input light 650. Inboth cases the effective transmission efficiencies are about 92% and theangular extents 652 (and 653) of the respective far field lightdistributions are +/−12 and +/−10 degrees respectively, FWHM as shownfrom the associated beam silhouettes 654 and 656. The far-field beamprofile half width 658 is designated in each case.

Far-field illumination results with lenticular diffusers are only aspredictable as this when the lenticular cross-sections are thinspherical shapes. When the lenticulars become aspheric and sag moredeeply, the paraxial approximation breaks down, and simple performancepredictions prove unsatisfactory. Computer simulations are required insuch cases to obtain reliable performance predications.

The actual behavior of aspheric lenticulars within the context of thepresent invention is demonstrated by the following set of examplescomprising shallow parabolic lenticulars, deeper parabolic lenticulars,prism-like hyperbolic lenticulars, mixed lenticulars and crossed(orthogonal) lenticulars. These examples uncover unique differences inlenticular illumination characteristics, unanticipated by prior art. Theexamples show that effective practice of the present invention dependson not only on selection of certain ranges of lenticular designparameters, but also on the lenticular orientation with respect to inputlight. The behavioral differences are quite striking, and lead to asubset of useful illumination profiles and patterns accessible withinthe present invention.

FIG. 24A provides perspective view of a typical parabolic (orhyperbolic) lenticular diffuser sheet 690 having parabollically-shapedlenticular elements. FIG. 24B shows the round-bottomed far field beamcross section that results when +/−5-degree×+/−5-degree collimated lightas from the light emitting system of FIG. 3A is applied to the planeside of a lenticular lens sheet having parabollically shaped lenticularelements with a relatively shallow sag. The lenticular elements 696within in FIG. 24A differ from those in FIG. 23B in that they arenon-spherical in cross-section and are somewhat more deeply sagged.

FIG. 24C shows the flat-bottomed far field beam cross section thatresults when +/−5-degree×+/−5-degree collimated light as from the lightemitting system of FIG. 3A is applied to the lens side of a lenticularlens sheet having parabollically shaped lenticular elements with arelatively shallow sag.

FIGS. 24B-24C illustrate the side elevations of a parabolic lenticularhaving peak to base ratio, SAG/PER=0.2. The parabolic focal point forthis condition is about 0.62 mm. Far field representations of the inputand output light are shown in silhouette above and below the lenticularsheet. When collimated input light 650 first strikes plane surface 692of the lenticular sheet 690, the resulting far-field output beamsilhouette 700 is symmetrical with angular extent 702 being +/22-degreesFWHM as shown. The corresponding center-weighted illumination pattern ona surface 1.5 m below the lenticular sheet has a width at half peak 4534of about 1.2 m, in close agreement with the silhouette's+/−22-degreeangular extent 702. For this orientation, the processed illuminationdisperses outwards from its central peak over a 2.6 m wide area 1.5 mbelow, as shown. When collimated light 650 first strikes lenticularsurface 698, however, a quite differently shaped beam profile (and fieldpattern) results. While the FWHM angular extent 708 remains about thesame, the output beam silhouette 710 has a flat-bottomed triangularshape that produces a square (or rectangular) field distribution withsharp angular cutoff. The resulting flat-topped field profile deploysalmost all output lumens within a 1.2 m wide region 1.5 m below. Thissharp cut-off behavior bares strong resemblance to the light emittingengine embodiments employing RAT reflectors by themselves, and isequally useful in many best mode practices of the present invention. Inboth orientations of this lenticular sheet 690, the effectivetransmission efficiency is about 92%.

FIG. 24D shows the wider-angled round-bottomed far field beam crosssection with satellite wings that results when +/−5-degree×+/−5-degreecollimated light as from the light emitting system of FIG. 3A is appliedto the plane side of a lenticular lens sheet having parabollicallyshaped lenticular elements with a moderately deep sag.

FIG. 24E shows the wide-angle flat-bottomed far field beam cross sectionthat results when +/−5-degree×+/−5-degree collimated light as from thelight emitting system of FIG. 3A is applied to the lens side of alenticular lens sheet having parabollically shaped lenticular elementswith a moderately deep sag.

FIGS. 24D-24E illustrate the side elevations of a parabolic lenticularhaving a somewhat larger peak to base ratio, SAG/PER=0.5. The parabolicfocal point for this case is about 0.25 mm. When collimated input light650 first strikes plane surface 692 this time, the far-field beamsilhouette 730 is practically unchanged in appearance, +/24-degrees FWHMas shown, but transmits only 51% of input light 650 in its main outputlobe 730. A portion of the remaining 49% is output uselessly in the weakhigh angle rabbit ear pattern shown, with the remainder trapped insidethe lenticular sheet by total internal reflections, some back reflectedtowards the input source. The illumination pattern that results is alsoabout the same as that shown for the shallower parabolic lenticulars inFIG. 24B. No such breakdown occurs when collimated input light 650 firststrikes the deeper parabolic lenticulars 734. The deeper paraboliclenses nearly double the far field angular extent from +/−22-degrees inFIG. 24C to +/−42-degrees in FIG. 24E. Moreover, the output beamsilhouette retains the flat-bottomed triangular cross-section it showedin FIG. 24C along with the correspondingly sharp angular cutoff. And,despite the considerably widened angular extent, transmission efficiencyis compromised, remaining at 92%.

FIG. 24F shows the wide angle tri-modal far field beam cross sectionthat results when +/−5-degree×+/−5-degree collimated light asillustratively from the light emitting system of FIG. 3A is applied tothe plane side of a lenticular lens sheet having parabollically shapedlenticular elements with a very deep sag.

FIG. 24G shows the very wide angle far field beam cross section thatresults when +/−5-degree×+/−5-degree collimated light as illustrativelyfrom the light emitting system of FIG. 3A is applied to the lens side ofa lenticular lens sheet having parabollically shaped lenticular elementswith a very deep sag.

FIGS. 24F-24G illustrate the corresponding diffusive properties of aneven deeper parabolic lenticular design, one having a peak to baseratio, SAG/PER=1.0, twice that of the example shown in FIGS. 24D-E. Theparabolic focal point for this ratio is about 0.125 mm. When input light650 first strikes plane surface 692, the effects from total internalreflections shown in FIG. 24D continues, with transmission efficiencyimproving slightly from 51% to about 70%, but with the output beam'scross-section 806 becoming strongly tri-modal showing three distinctillumination peaks in the far field illumination pattern. Tri-modallight distributions may be used to spot light (or flood light) a centrallocation and two satellites. The far field behavior shown with the lensup lenticular orientation in FIG. 24G demonstrates that sharply cutoffeven illumination 820 is possible with this lenticular diffuser 808 outto 120-degrees full angle without compromise. Despite so wide an angularcone 813 where some refractive recapture of higher angle output light byneighboring parabolic lenticulars is inevitable, net transmissionefficiency only drops to 86% and output light continues to show thecharacteristic flat-bottomed triangular beam silhouette 820 associatedwith such lens up lenticular orientation.

FIG. 25 is a graph summarizing the best mode geometric relationshipfound to exist between total far field angle 870φ, (measured FWHM 872)and the parabolic lenticular peak-to-base ratios (SAG/PER) between 0.1and 1.0, for lenticular diffuser sheets 874 of all types within thepresent invention. These results occur only for the special case whenthe lenticular curvatures are made to face towards collimated inputlight 650. The applicable peak-to-base ratio range, 876, is consideredunique in that net transmission efficiency remains above 86% throughout,and is 90% or greater between SAG/PER=0.1 and SGA/PER=0.75. Far fieldbeam cross-sections, represented by silhouettes in FIGS. 24C, 24E, and24G, maintain their substantially flat-bottomed triangularcharacteristics throughout the entire range as well.

The functional relationship graphed in FIG. 25 is non-linear and notpredicted mathematically by any simple theory. A reasonable linearapproximation is provided approximately in equation 8 for lenticulardiffuser sheets made of polymethyl methacrylate (acrylic), n=1.4935809,and in equation 9 for sheets made of polycarbonate, n=1.59. Lenticulardiffuser sheets 874 used in practice of the present invention may bemade of any suitable optically transparent polymeric (or glass)material, but those with refractive indices nearer to that of acrylicare better at suppressing transmission losses due to total internalreflection. Lenticular diffuser sheets 874 made of polycarbonate,n=1.59, are better at achieving wider far field angles at smallerpeak-to-base ratio. One example of this is difference is that aparabolic lenticular made of acrylic achieves a far field angular extentof 120-degrees full angle with a peak-to-base ratio, SAG/PER of about0.63, whereas its polycarbonate counterpart does so with a SAG/PER ofabout 0.525, which reduces the necessary parabolic aspect ratio by about20%. The cost of this particular comparison is only about 2% in nettransmission efficiency, which is probably inconsequential for mostapplications.

φ=172.24[SAG/PER] ^(0.38)−48.5(8)  (8)

φ=203.15[SAG/PER] ^(0.45)−46.66  (9)

It is important to point out that hyperbolic lenticulars of any designdo not develop the favorable flat-bottomed triangular far field beamcross-sections of FIGS. 24C, 24E, and 24G whether their lenticularspoint towards the source of collimated input light 650, or away.

FIG. 26 shows a perspective view of thin profile illumination system 1of the present invention along with one sheet of lenticular anglespreading film 874 with its spreading power in the X meridian, itslenticules facing towards the incoming lighting from light guiding platesubsystem 110, as suggested by the findings of FIGS. 24C, 24E, 24G andthe summarizing graph of FIG. 25.

FIG. 27 shows one illustrative result with illumination system 1 of FIG.26 placed at a 1500 mm height above the 1800 mm×1800 mm surface to beilluminated. The computer simulated field pattern 880 is spread about+/−30-degrees along x-axis 7, but remains about +/−5-degrees alongy-axis 5. The center of the 57 mm×57 mm luminaire is shown as 882. Thisresult has been validated experimentally using embossed lenticular filmof the equivalent design.

FIG. 28 shows a perspective view of thin profile illumination system 1of the present invention along with two orthogonally directed sheets oflenticular angle spreading film 874 (and 875 the same design as 874)with its spreading power in the X meridian and in the Y meridian, withboth sheet's lenticules facing towards the incoming lighting from lightguiding plate subsystem 110, as suggested by the findings of FIGS. 24C,24E, 24G and the summarizing graph of FIG. 25.

FIGS. 29A-29B shows two illustrative results with thin illuminationsystem 1 of FIG. 28 placed at a 1500 mm height above the 1800 mm×1800 mmsurface to be illuminated. The computer simulated field patterns 884(FIG. 29A) and 886 (FIG. 29B) are spread about +/−30-degrees along bothx-axis 7 and y-axis 5 in FIG. 29A, and about +/−15-degrees in FIG. 29B.The centers of the 57 mm×57 mm luminaire are shown as 882. These resultshave also been validated experimentally using embossed lenticular filmsof the equivalent design.

Total effective field efficiency for the single-emitter luminaireformat, without use of angle-spreading film, is 0.74 (0.86 for taperedinput bar and 0.86 for tapered plate) with antireflection coatingsapplied to the input aperture of both bar and plate. Field efficiencydrops to 0.67 without input coatings (0.82 for tapered bar and 0.82 fortapered plate). Both types of spreading films (lenticular anddiffractive) have net transmission efficiencies of >0.9, and therebyreduce the system's net field efficiencies by 0.9 for one spreading filmand by 0.81 for two.

Field efficiency for the higher-output multi-emitter luminaire format asdescribed in FIGS. 2A-2C is better because the output efficiency of thearray-type light engine is about 10%-15% higher than that of thetapered-bar light engine. Net field efficiency for the higher-outputsystem is 0.82 without use of angle-spreading film (0.95 for thearray-type light engine and 0.86 for the AR-coated tapered plate).

These field efficiencies are quite comparable to the total luminaireefficiencies provided by the traditional 2′×2′ fluorescent troffers usedcommonly in commercial overhead lighting treatments, ranging between 0.5and 0.7 depending on design.

A greater efficiency advantage is realized in task lighting applicationswhere premium value is placed on lumens delivered to a particularcircular, square or rectangular field area.

While it may be of growing economic and environmental importance toachieve luminaires with higher energy efficiency, it is also importantto enable meaningful reductions in size and weight. Smaller and thinnerluminaires provide lighting architects with new design alternatives, butprovide commercial builders and their lighting installers withpotentially less labor-intensive (and costly) installation requirements.

FIG. 30A provides an exploded top perspective view 890 of one example ofa fully configured light engine embodiment of the present inventionbased on the functional illustrations of FIGS. 1A-1D, 3A-3E, 4, 16A-16B,26, and 28. This fully configured light engine form is as also describedin U.S. Provisional Patent Application Ser. No. 61/104,606. FIG. 30Bprovides a magnified perspective view 892 of the coupling regionexistent between a commercial LED emitter 904 that can be used, thecorresponding square or rectangular RAT reflector 906 and tapered lightguiding bar 100 with light extraction film 102, according to the presentinvention as was referenced in U.S. Provisional Patent Application Ser.No. 61/104,606. The core light generating sub-system 900 consists ofillustrative heat sink element 902, commercial 4-chip LED emitter 904(OSTAR™ model LE W E2A as made by Osram Opto Semiconductors), RATreflector 906, 62 mm long tapered light guiding bar 110 with 57 mm longemitting length, facetted light extraction film 102, 57 mm×57 mm taperedlight guiding plate 112, facetted light extraction film 114,illustrative plastic (or metal) chassis frame 908, illustrativeattachment hardware 910-918, illustrative heat spreading circuit plate920, and illustrative electronic circuit elements 921 (with someindividual examples being 922-927). This illustrative fully configuredlight engine embodiment as shown is pre-assembled for example by boltingLED emitter 904 to illustrative heat sink element 902 with two pan-headscrews 910 (and 911, not labeled). Heat sink element 902 may have anyconfiguration designed for effective heat extraction from LED emitter904 (effective heat extraction improves LED performance), including, forexample, spreading over the entire topside of the light engine much asthe heat spreading circuit plate 920. The RAT reflector 906, and lightguiding pipe 100 with attached light extracting film 102, are installedinto illustrative plastic (or metal) chassis frame 908, followed by theequivalent insertion of tapered light guiding plate 112 with itspre-attached light extraction film 114. This is followed by theattachment of illustrative heat sink element 902 with pre-attached LEDemitter 904 to the edge of illustrative plastic (or metal) chassis frameusing illustratively 4-40 screws 912 and 913. Core light generatingsub-system 900 is then attached to illustrative heat spreading circuitplate 920 using illustrative hold down hardware 914 and illustrative4-40 screw 915 as along guideline 932 plus using 4-40 screws 917-918 andpan-head screw 919. The illustrative heat spreading circuit plate may bebrought into thermal contact with heat sink element 902, mechanically orvia thermal coupling compound, in order to improve dissipation of heatfrom the LED and/or the other electronic components. The illustrativeheat spreading circuit plate may contain all necessary electronic andelectrical interconnection elements, collectively represented as 921,that may be needed to bring either high voltage AC or low-voltage DCpower directly to the positive and negative terminals of LED emitter904, via associated voltage regulation components 927, local powercontrolling elements 935 and illustrative electrical connection straps936-940 required to complete the associated circuit involved. In thisexample, electrical components 922-931 are shown illustratively ascapacitor 922, microprocessor (integrated circuit or applicationspecific integrated circuit) 923, resistor 924 (not labeled), capacitors925-926, and voltage regulating MOSFET 927. Various combinations ofelectronics components like these (and others) may be used discretely orfunctionally integrated to perform a wide variety of effective powercontrolling functions for associated LED emitter 904, including digitalprocessing and associated response to internal or external LED emitterpower control signals.

FIG. 30A also shows symbolic representation of the light engine'sinternally interrelated light flows as described earlier in FIG. 1C. Theinput aperture of RAT reflector 906 collects substantially all outputlight 950 generated by LED-emitter 904. RAT reflector 906 is shown inthis example as a hollow reflector element placed just beyond theillustrative emitter's individual LED chips (but may be replaced byother optical elements including one or more of a lens, a group oflenses, a refractive reflector, a light pipe section, a hologram, adiffractive film, a reflective polarizer film, and a fluorescent resinwhose combination transmits substantially all light 950 into lightguiding bar 100 with desired control of the associated beam angles).

Furthermore, the LED emitter 904 (and LED emitter 1000 in FIGS. 31A-31Cand 33A-33C further below) may have a different form of light-emittingsurface than that shown in the present examples (these light emittingsurfaces being the flat exterior surface of a clear encapsulantsurrounding the LED chips). The LED emitter's light emitting surface mayalso be as a raised phosphor coating, a raised clear encapsulant, araised phosphor or clear encapsulant with micro-structured exteriorsurface, or a raised phosphor or a clear encapsulant withmacro-structured surface. Some of these equally applicable variationsmay allow for more total emitted light and/or more effective lightcollection by RAT reflector 906 and/or its optical equivalent. Such adifferent light-emitting surface may also be a secondary optic coupledto the clear encapsulent around the LED chips, such as, for example, adome lens like those commonly provided by Osram Opto Semiconductor andmany other similar LED manufacturers.

In the manner shown, a substantial percentage of output light 950 fromLED emitter 904 enters the input face of light pipe 100 as light beam952, and while inside undergoes total internal reflections within it. Ahigh percentage of light 952 is thereby turned 90-degrees bydeliberately planned interactions with micro-facetted light extractionfilm 102 as explained earlier (e.g., FIGS. 11A, 12B and 12C) and isthereby extracted uniformly from the pipe along its associated 57 mmeffective running length and ejected into air as beam 954, which in turnenters the input face of light guiding plate 112. These light flows areshown in more detail in the magnified view of FIG. 30B. Light-flow 954undergoes further total internal reflections within the light guidingplate 112 and its attached facetted light extraction film 114 and isturned 90-degrees and extracted into air evenly across the plate'ssubstantially square light distributing aperture 956 (shown more clearlyin the perspective view of FIG. 30C), thereby providing the lightengine's practical source of directional output illumination 960.

FIG. 30B is a magnified perspective view of only dotted region 892 asreferenced in FIG. 30A, providing a more detailed view of the keyelements of the engine's three-part LED light emitter sub-system(comprising illustrative 4-chip LED emitter 904, etendue-preserving RATreflector 906, and tapered light guiding pipe 100 with facetted lightextraction film 102). In this LED emitter example, there are four 1 mmsquare chips 964 arranged in a 2.1 mm×2.1 mm pattern (inside largerdielectrically-filled cavity frame 963 surrounding the chips). Other LEDchip and encapsulating dielectric combinations are as easilyaccommodated by variations on this design, including Osram's six-chipOSTAR™ versions. Positive and negative electrodes 966 and 967 areconnected to the appropriate electronic delivery members provided withinillustrative heat spreading circuit plate 920 and its illustrativeelectronic circuit elements 921, as in FIG. 30A. The commercial OSTAR™ceramic package 970 is hexagonally shaped as supplied by Osram and hasbeen trimmed to parallel surfaces 971 and 972 without electricalinterference to better comply with thinness requirements of the presentinvention. Mounting holes 975 are used for heat sink attachment, asshown above via low-profile pan-head mounting screws 910-911 (neithershown). This illustrative RAT reflector element 906 has three sequentialsections, each having square (or rectangular) cross-section. Firstsection 974, placed only for this illustration only, slightly beyond thefour OSTAR™ chips. In typical practice of the present invention, thissection is placed as near to the four OSTAR™ chips as mechanicallypermitted. Section 974 is etendue-preserving, in that its designed tocollect substantially all light emitted by the group of chips at itsinput opening, with each of its four reflective sidewalls shaped asdictated by the Sine Law's input and output boundary conditions, toconvert the collected angular distribution by internal reflections ineach meridian, optimizing the entry angles to the input face (not shown)of tapered light guiding pipe 100. Second section 976 and third section978 surround the illustrative 3 mm×3 mm entrance face of light guidingpipe 100 as one way of facilitating mechanical mounting and alignment.Neither section 976 or 978 has any optical function or special shape,and may be eliminated.

In best practice, tapered light guiding pipe 100 is injection molded.All mold tool surfaces in this case are provided a featureless polishedmirror finish. Molding materials are of optical grade, preferablyoptical grade PMMA (i.e., polymethyl methacrylate) or highest availableoptical grade polycarbonate obtainable to reduce its intrinsicallyhigher bulk absorption loss. In addition, the corners and edges of lightguiding pipe 100 are to be made as sharply as possible to minimizescattering loss from of by roughened edges, to minimize unwanted TIRfailure, and to maximize the edge-to-edge optical coupling with thefacetted light extraction film 114. Facetted light extraction film 114is attached, as described earlier, to the back surface of pipe 100 bymeans of a thin clear optical coupling medium 320 as in FIG. 11A (e.g.,pressure sensitive adhesive). In this form, the light extracting facets322 are made of either PMMA or polycarbonate (e.g., by embossing,casting, or molding) and then coated with high reflectivity enhancedsilver (or aluminum) 340.

FIG. 30C provides a perspective view of the completely assembled form ofthe fully-configured light engine embodiment shown in exploded detail890 in FIG. 30A, as this present invention was described in U.S.Provisional Patent Application Ser. No. 61/104,606. Total enginethickness is determined primarily by the thickness of illustrative heatsink element 902 and any additional net thickness associated with theattachment of illustrative heat spreading circuit plate 920. Thecollimated down light illumination that develops projects evenly fromsubstantially the entire square (or rectangular) output aperture area934.

FIG. 30D illustrates a related geometric form of the present inventionin which metal coated facetted layer 102 may be replaced by planereflector 274 (as in FIG. 8A) and a separate facetted light extractionelement 103, similar to 104 but having uncoated facets of anappropriately different geometrical design placed just beyond the frontface of pipe 100 (facet vertices facing towards the pipe surface). Lightflow 952 internal to pipe 100, in either form, induces sequentialleakages from the pipe itself that on interaction with the facets 322(see FIG. 11A-11C) of facetted light extracting film used causesequentially distributed output light 954 in a direction generallyperpendicular to the front face of pipe 100.

FIG. 30E is a perspective view showing the variation of FIG. 30D appliedto light guiding plate 112. In this form of the present invention areflective layer 980 (similar to 274) is placed on (or slightlyseparated from) the topside surface of light guiding plate 112, and aseparate facetted light extraction sheet 982 (similar to 103) placedjust beyond the plate's opposing side light output surface. Thisillustration is provided to show a variation of the alternative lightguiding, extracting and collimating form as illustrated in FIG. 30Dapplied to a light guiding plate 112 rather than to a light guiding pipe100. Edge emitted output light beams 954 from the illustrativecollimating light bar system example composed of light guiding pipe 100and light extraction film 103 (or, as another example, from thecollimating light bar system illustrated previously in 30B composed oflight guiding pipe 100 and light extraction film 114) enter the inputedge of light guiding plate 112 and as a result of passage through theplate system, are extracted across nearly the entire output aperture ascollimated output beam 960.

In this form of the present invention, collimated light (not shown)extracts obliquely from tapered plate 112 and mirror 980 into the thinair region below plate 980 and above facetted film 982 (as was shownpreviously in FIGS. 7A-7C), and then redirected as output down light bypassage through facetted film 982.

Another practical form of the present invention as illustrated in FIG.30D arises when facetted film 982 is removed. This results in a beam oflight emanating from the full surface of plate 112 having theobliquely-angled pointing direction shown in FIG. 7C, a useful behaviorthat will be described further below.

The general form of the present invention illustrated in FIGS. 30A-30D(as in FIGS. 1A-1D, 3A-3E, 4, 16A-16B, 26, and 28) employs a taperedlight guiding pipe 100 to collimate LED input light in one meridianwhile presenting that light as input across the edge of a tapered lightguiding plate deployed to preserve the collimation of the lightreceived, while collimating that same light in its orthogonal meridian,so as to produce completely collimated output illumination.

An alternative form of the present invention was introduced in FIGS.2A-2E, replacing the tapered light guiding pipe 100 and its associatedelements with a reflector-based alternative. A linear array of one ormore etendue preserving RAT reflectors was arranged to collimate LEDinput light in one meridian while presenting that light as input acrossthe edge of a tapered light guiding plate 112 arranged to preserve thereflector-based collimation of the light received, while collimatingthat same light in its orthogonal meridian, so as to produce completelycollimated output illumination.

FIGS. 31A-31D illustrates a practical implementation of this form of thepresent invention.

FIG. 31A provides an exploded top perspective view of a practical singleemitter segment 998 (following the general example of FIG. 2A) for afully configured multi-emitter light engine embodiment of the presentinvention based on this etendue-preserving RAT reflector-based means ofproviding partially collimated light input to a light guiding plate.This embodiment example illustrates use of a six-chip LED emitter 1000manufactured by Osram Opto Semiconductor, e.g., Model LE CW E3A, mountedon the same hexagonal substrate as shown above, and trimmed torectangular shape in a manner also shown above. LED emitter 1000 in thisan ensuing examples may have a different form of light emitting surfacethan that shown as was discussed above. Such a different light-emittingsurface may be a secondary optic coupled to the clear encapsulent aroundthe LED chips, such as, for example, a dome lens like those commonlyprovided by OSRAM and many other LED manufacturers. Other variations,too numerous to illustrate, only compliment practice of the presentinvention.

In this illustration, LED emitter 1000 is attached to illustrative heatsink element 1002 using two pan-head screws 910 and 911 as was shown inFIG. 30A. The form of heat sink 1002 indicates one possible arrangementof heat extraction fins 1003 for efficient heat removal by ambient airpassing between them. Heat sink 1002 may have any configuration designedfor effective heat extraction from LED emitter 1000 (effective heatextraction improves LED performance), including, for example, spreadingover the entire topside of the light engine and/or along its sides.Wide-angle light emission from the 6 chips of LED emitter 1000 iscollected by the similarly sized input aperture of etendue-preservingRAT reflector 1004. RAT reflector 1004 is constructed for this examplein four principal parts, two identical side elements 1006 and 1008,whose highly polished sidewall mirrors 1010 and 1012 form two opposingsides of the associated reflector's four-sided rectangularcross-section, and two identical top and bottom elements 1014 and 1016whose highly-polished reflecting surfaces 1018 and 1020 complete thefour-sided reflector's rectangular cross-section. The four constituentparts of RAT reflector 1004 may be attached by adhesive, may be weldedor soldered together, and as illustrated, may be bolted together usingrecessed screws 1022-1025 which pass through through-holes made in toppart 1016 and are received by correspondingly tapped holes in bottompart 1014. Four higher precision dowel pins 1028-1031 (within only 1028labeled) may be used for additional accuracy in reflector alignment.Then, one way of assuring proper alignment between the rectangularoutput aperture of RAT reflector 1004 and the input edge of taperedlight guiding plate 1034 is illustrated in this example by addingreflector overhang portions 1036 and 1038, reflective gripping plates1040 and 1042, and set screws 1044 and 1046 which apply sufficientholding pressure to gripping plate 1042 (and thereby to light guidingplate 1034) via tapped holes 1048 and 1050.

In the illustration of FIG. 31A, light guiding plate 1034 is similar toplate 112, but in this case is made narrower in width than in length tomatch the output aperture size of RAT reflector 1004, enabling efficientlight power transfer from RAT reflector to light guiding plate andfurther enabling uniform plate light extraction (compared to, say, amuch wider plate which would have dark bands outside the cone of lightemitted by the RAT in XY meridian). The example of FIG. 31A showsfacetted light extraction film 1035 (similar in design to 114) affixedin the manner described to the topside of light guiding plate 1034.Alternately, as shown in the optional extracting form of FIG. 30D,facetted film 1035 may be replaced by a plane mirror, and anotherfacetted film similar to 982 may be placed instead just below outputplane 1052 of light guiding plate 1034.

FIG. 31B is a perspective view of the assembled version of the practicallight engine example shown exploded in FIG. 31A. Illustrative RATreflector 1004 assembles along dotted lines 1054 and 1056. Heat sink1002 with attached LED emitter 1000 bolts to RAT reflector 1004 using,for example, two diagonally deployed attachment screws 1058 (shown) and1060 (hidden). When positive and negative DC supply voltage is appliedto positive and negative terminal wires 1062 of LED emitter 1000, lightflows as has been explained from LED emitter 1000 through RAT reflector1004, into and through light guiding plate 1034, and becomes doublycollimated output beam 1064 (similar to doubly collimated far-fieldillumination 10 as shown in FIG. 2A) with angular extent in theZX-meridian, +/−θ_(X), being set by the collimating characteristics oftapered light guiding plate 1034 (and any ancillary characteristicsimparted by facetted light extraction film 1035), and with angularextent in the ZY-meridian, +/−θ_(Y), being set by the collimatingcharacteristics of etendue-preserving RAT reflector 1004 established byits output aperture in the XY plane.

In the present example, RAT reflector 1004 is matched to dimensions ofthe six-chip Osram OSTAR™ Model LE CW E3A with an input aperture that isapproximately 2.2 mm along Z-axis 6 and 3.6 mm along Y-axis 5. It is the3.6 mm input aperture dimension that drives the RAT reflector's outputaperture width that is further matched to width 1068 of light guidingplate 1034 being used to achieve an angular extent 71 that is desired.

FIG. 31C is a schematic top view providing a clearer description of theunderlying geometrical relationships that are involved in matching LEDemitter 1000, RAT reflector 1004 and light guiding plate 1034. FIG. 31Cis schematic a top cross-sectional view of the angle transformingreflector arrangement shown in FIGS. 31A-31B along with LED emitter1000. In this illustration, the reflector's top element 1016 (and itsillustrative attachment screws 1022-1025) are removed to reveal theunderlying geometrical relationships controlled by equations 10 and 11(in terms of the reflector element's input aperture width 1070, d₁, itsideal output aperture width D₁, its ideal length L₁, and its idealoutput angular extent +/−θ₁), with +/−θ₀ being the effective angularextent of the group of LED six chips 1071 in illustrative LED emitter1000 (effectively +/−90-degrees). Similar relationships, equations 12and 13, govern the orthogonal meridian's ideal geometry d₂, D₂, L₂, andθ₂, but are not illustrated graphically. In this case, interchangeably,θ₁ represents θ_(X) and θ₂ represents θ_(Y). The symmetrically disposedreflector curves 1072 and 1073 of reflector section 1074 as shown inFIG. 31C are ideal in that their curvatures satisfy the boundaryconditions given by equations 10 and 11 at every point. Section 1074only shows the initial length 1076, L₁₁, of an otherwise ideal reflectorlength L₁. Initial length L₁, is expressed as f L₁, where f is afractional design value typically greater than 0.5 (e.g., f=0.62 in thepresent illustrative example).

d ₁ Sin θ₀ =D ₁ Sin θ₁  (10)

L ₁=0.5(d ₁ +D ₁)/Tan θ₁  (11)

d ₂ Sin θ₀ =D ₂ Sin θ₂  (12)

L ₂=0.5(d ₂ +D ₂)/Tan θ₂  (13)

It's usually a reasonable approximation in practice that Sinθ₀˜90-degrees, especially with the LED light emitters used in accordancewith the present invention. The ideal reflector lengths L1 and L2 can beexpressed more compactly, in this case, as in equations 14 and 15.

L ₁=0.5d ₁(Sin θ₁+1)/(Sin θ₁ Tan θ₁)  (14)

L ₂=0.5d ₂(Sin θ₂+1)/(Sin θ₂ Tan θ₂)  (15)

A unique design attribute of this particular reflector fed light engineexample is that the angular extents of the output illumination 1064 ineach output meridian (+/−θ₁ and +/−θ₂) are completely independent ofeach other. The reflector geometry developed in FIG. 31C (i.e., meridian1) determines the engine's output angular extent (+/−θ₁ or +/−θ₁₁) inonly that one meridian. The engine's output angular extent in the othermeridian (+/−θ₂) is determined substantially by the (independent)behavior of the tapered light guide plate 1034 and associated facettedfilm sheet 1035).

Matched to the illustrative six-chip Osram LED emitter 1000, d₁=3.6 mm,as set by the size, spacing and surrounding cavity of Osram's threeinline 1 mm LED chips, +/−θ₁=+/−10.5-degrees by design choice, so D₁(from equation 10) becomes in this case approximately3.6/Sin(10.5)=19.75 mm, and the ideal reflector length L₁ associatedwith these conditions becomes (from equation 11) 0.5(3.6+19.75)/Tan(10.5)=63.0 mm. The choice of 10.5-degrees is onlyillustrative. There are many other practical design angles to choosefrom, most efficiently those wider than 10.5-degrees.

Optical ray trace simulations (using the commercial ray tracing softwareproduct ASAP™ Advanced System Analysis Program, versions 2006 and 2008,produced by Breault Research Organization of Tucson, Ariz.) have shownthat ideal reflectors of this type (governed the Sine Law equations10-13) can be trimmed back in length from their ideal, L₁, withoutincurring a significant penalty in their effective angle transformingefficiency (or output beam quality). And, when used in the present lightdistributing engine arrangement, which preferably deploys anglespreading output aperture films such as have been described previously(e.g., the parabolic lenticular lens sheets shown FIGS. 24A-24G and 25)the tolerance to such deviations in design from ideal dimensions becomesless critical. Accordingly, in the present example, theetendue-preserving RAT reflector unit (1004) has been reduced in lengthby 38%, to a total length, L₁₁ (as shown in FIG. 31C), of 39 mm. As aresult, illustrative LED input ray 1080 is reflected from reflectorcurve 1073 at point 1082 and strikes symmetrically disposed reflectorcurve 1072 at point 1084, reflecting ideally outwards without anadditional reflection as output ray 1086 of LED light emitter 1000,making the intended output angle θ₁ (1088) with reflector axis line1090.

The small deviation from ideality tolerated with the reflector lengthreduction as shown in the example of FIG. 31C is indicated by thetrajectory differences between LED input ray segments 1092 and 1094(dotted). The trajectory of ray 1092 (angle θ₁ with axis line 1088) isdetermined by the ideal (etendue preserving) reflector length L₁ and theideal output aperture width D₁, such that by geometry, Tan θ₁=(D₁/2)/L₁,set by choice to 10.5-degrees in the present example. The devianttrajectory of ray 1094, however, is set by the reduced length 1074, L₁₁,and the proportionally reduced output aperture width 1096, D₁₁, as Tanθ₁₁=(D₁₁/2)/L₁₁. In this example, L₁₁=39 mm and D₁₁=18.75 mm, soθ₁₁=13.5-degrees, which is only a small degree of angular deviation, andinconsequential to most commercial lighting applications of the presentinvention. Furthermore, it is only a fraction of the total rays thatfall into this deviation, whereas a significant fraction remain withinthe ideal output range +/.+−.θ₁.

Whenever more sharply cut-off angular illumination is required usingthis form of thin-profile reflector fed light engine (as in FIGS. 2A-2E,and 31A-31B), a lesser degree of reflector truncation may be employed.

The RAT reflector's design in the orthogonal meridian (+/−θ₂) is made todeliberately pre-condition light for optimum coupling efficiency to thecorresponding entrance face of light guide plate 1034 and its associatedfacetted light extraction film 1035). Preferable angular conditions forthis purpose as described earlier (e.g., FIGS. 3D-3E, and 5A-5C), are+/−50-degrees and +/−55-degrees (in air) for a 3 mm thick tapered lightguiding plate 112 having a 3-degree taper-angle made of highest opticalgrade transparent plastic or glass.

FIG. 32A shows simplified example of a multi-emitter embodiment of thepresent invention, following its general introduction in FIGS. 2A-2E,and in FIGS. 31A-31C above. Practical packaging details related to heatsinks, the LED emitter's electrical interconnection substrate, and themeans with which each light engine segment is attached to adjacentsegments and to the associated light guiding plate 1034 is omitted inthis example for visual clarity. This particular example deploys sevenparallel input emitting channels, shown co-joined to one another to forma single input source 1098 to the same type of tapered light guidingplate 112 or 1034 illustrated earlier in FIGS. 3A-3B, 4, 26 and 28. Thetop reflector sheet that covers the seven individual input reflectorelements has also been left out for visual simplicity. For this example,the operative RAT reflector is matched for use with the four-chip OsramOSTAR™ model LE W E2A as was used in the example of FIG. 30A. Thecorresponding input aperture 1070 in FIG. 31C is 2.2 mm. Only thefour-chip frame portion 964 (as referenced earlier in FIGS. 30B and 30D)of LED emitter 904 is shown in the present illustration for additionalvisual clarity. If the associated RAT reflector's design angle, θ₁ as inFIG. 31C, is made a wider one for this example at +/−15-degrees, thecorresponding output aperture size, D_(I), without the reflector lengthtruncation applied in FIG. 31C, becomes by means of equation 10,(2.2)/Sin(15) or 8.5 mm (along the plate system's input edge, also thesystem's Y axis 5). The orthogonal pair of reflector sidewalls (1014 and1016 as in the example of FIG. 31C) convert the +/−90-degree input lightfrom the four-chip LED emitter being used to the narrower angular rangein the system's XZ meridian (e.g., +/−52.6-degrees) preferred by lightguiding plate 1034. When seven such emitter-reflector combinations areplaced adjacent (or nearly adjacent) to each other as illustrated inFIG. 32A, the collective length they occupy along the systems Y-axis 5is a minimum of 59.5 mm. Matching efficiently to this width requiresusing a light guiding plate 1034 whose width along the system's Y-axis 5is at least 59.5 mm.

For those lighting applications requiring higher lumen levels, thissegmented array-type input engine 1098 is especially useful. The7-emitter example shown is about as thin as earlier single emitterembodiments shown. One advantage of this form is that with sevenseparate LED emitters the collective engine is able to supply up toseven times the net lumens supplied by each LED emitter that is beingused. If the total emitted lumen output of the four-chip LED emitter isfor example taken as 400 lumens, the net throughput efficiency of eachRAT reflector segment, 93%, and the net throughput efficiency of taperedlight-guiding plate 1034, 86%, then the total lumen far-field output forthe thin illumination system 1 becomes (7)(400)(0.93)(0.86) or 2,240lumens.

Another advantage of the multiple-emitter system is that the same lumensas a 1-emitter system can be achieved at lower operating current, whichresults in higher power efficiency (lumens/Watt) operation because LED'sgenerally operate more efficiently at lower currents. This can alsoimprove the system's lifetime, as the LED's will degrade more slowlywhen operated at lower currents. Furthermore, in a multiple emittersystem, some LED's can be left entirely off for some period (as long asuniform emission across the entire plate is not required), therebysaving them for future use, which can further increase the lifetime ofthe whole system. As one simple example, by using a 7-emitter system ina lighting application where one LED can produce sufficient lumens forthe application, the other six LED's can be left off and usedsequentially as each LED fails, effectively increasing the lifetime ofthe system by 700%. Performance consistency can be achieved by turningon one LED gradually as another gradually fails.

Yet a further advantage of a multiple-emitter system is that a wideroverall range of dimming levels. Also, a wider overall range of colorand color mixing options are possible through use of different colorLED's.

FIG. 32B is illustrates a perspective view of the system in FIG. 30A,with top reflector 1108 added, and also includes an example of thesystem's realistically computer-simulated output beam profile for thedesign parameters involved. The far field output 1110 developed by thishigher output embodiment of the present invention has a net far-fieldangular distribution that is +/−15-degrees by +/−5-degrees with the samerectangular field pattern characteristics as seen for the earlierillumination system embodiments.

Numerous practical forms of the present invention may be developed asvarious groupings of the basic single-emitter engine segment shown firstgenerally in FIG. 2A, and then as more detailed segment 1037 in FIG.31B. A few illustrative embodiments of engine groupings are shown inFIGS. 33A-33C.

FIG. 33A shows a topside perspective view of two side-by-sidedown-lighting engine segments 1037 of emitter-reflector-light guidingplate thin illumination system invention variation as illustrated inFIG. 31B.

Frame 1120 is added as a secure packaging for light guiding plate 1034and its associated light extraction film 1034, as well as any lightshaping films not shown. The uniformity of far-field illumination isunaffected by the framing of the light guiding plate apertures. In thepresent example, the framing width 1122 is arbitrarily made 3 mm, butcould be more or less as desired. The clear illuminating apertures inthis illustration are about 57 mm×18.75 mm. Illustrative heat sinkelements 1002 each extend 24.35 mm beyond each LED emitter 1000 attachedto them but in other configurations could extend longer and/or run overthe top of the engine and/or its sides. The total length of this engineexample, end-to-end, is about 128 mm, and the total two-engine outsidewidth is 49.54 mm. Maximum thickness, 15 mm in this example, is limitedby the mechanical-design of the Osram OSTAR™ ceramic substrates used(which were sliced down to 15 mm as shown).

Actual prototype engines have been made to this exact design, and theirmeasured laboratory performance agrees closely with performancepredictions of throughput efficiency and far-field beam profiles made bycomputer simulation using the salient parameters described above.

FIG. 33B shows a topside perspective view of two in-line down-lightingtwo-engine segments of the emitter-reflector-light guiding plate thinillumination system invention variation as illustrated in FIG. 31B.

FIG. 33C shows a topside perspective view of two counter-posedtwo-engine segments 1037 of the emitter-reflector-light guiding platethin illumination system invention variation as illustrated in FIG. 31B.

Many other combinations and variations are equally possible in practiceof the present invention. The combination of multiple engines (whetherof the engine types shown in FIGS. 31-33, or the engine types shownpreviously) also allows variety of functions within a single system,such as variety in pointing direction and angular extent. For example,one of the engines could point light toward a wall while another pointslight downwards. As another example, one engine could project light in a+/−5-degree square cone, while another projects light in +/−20 degreecircular cone. Many multi-functional combinations and variations havebeen and could be imagined. Some have been described in a related U.S.Provisional Patent Application Ser. No. 61/104,606.

Light guiding plates 112 and 1034 used in all examples of the presentthin illumination system invention herein share a tapered cross-sectionthat's been extruded linearly along one Cartesian axis (e.g., Y-axis 5).The associated facetted light extraction films, whether attached to oneside of the light guiding plate's tapered cross-section, as shown inFIG. 11A, or as a separate facetted element, separated slightly from thelight guiding plate's tapered cross-section, as shown in the perspectiveview of FIG. 30D, are extruded linearly along the same Cartesian axis(e.g., Y-axis 5). The result in both cases is a constant cross-sectionalong the axis of extrusion.

FIG. 34A is a schematic perspective illustrating execution of the globalboundary condition for linear extrusion of the tapered light guidingplate (112 and 1034), wherein the normal to prototype taperedcross-section 1128, vector 1130, follows a straight axial extruding line1132, illustratively parallel to the system's Y-axis 5. Such linearlyextruded plates are used in the examples of FIGS. 3A-3B, 5A, 7A-7C,8A-8D, 9, 11A, 12B-12E, 13A-13C, 16B, 26, 28, 30A, 30E, 31A-31B,32A-32B, and 33A-33C. Cross-sectional shape and dimensions are heldconstant, as illustrated by the reference cross-sections 1134-1140.Extruded boundary surface 1142 becomes the light input plane or face ofthe extruded light guiding plate. Line 1144 is the tapered light guideplate's mathematically idealized knife-edge. In practical production,the actual knife-edge is an approximation, as was shown in FIG. 5A.

FIG. 34B shows in schematic perspective that the linear boundarycondition of FIG. 34A also forms the linearly extruded facetted lightextraction films under the present invention as were shown in FIGS.3A-3B, 4, 26, 28, 30A, 30D, 31A, 31D, 32A-32B, and 33A-33C. Prototypefacet cross-section 1146 follows the same direction vector 1130 for itsextrusion along straight axial extruding line 1132 as is shown in FIG.34A for the linearly extruded tapered light guiding plate.

Not all useful light guiding plates and facetted light extraction films(and means to couple the plates and films together) under the presentinvention are extruded linearly. Radially extruded light guiding platesand radially facetted light extraction films enable circular, as well asalternatively square and rectangular forms of thin illumination systeminvention. In these radially extruded forms, input light from one ormore LED emitters is applied to a cylindrical light guide edge ratherthan to a linear one.

FIG. 34C illustrates in schematic perspective a basic execution of theradially constrained extrusion to form disk-type tapered light guidingplates under the present invention. Prototype tapered cross-section 1128is extruded about an axis line 1148 (running parallel to system Z-axis6) such that the cross-section's prevailing direction vector 1150follows circular guide path 1152. As this constant cross-section lightguiding solid plate is developed, a cylindrical bounding surface 1154 isformed in the center, and a mathematically idealized circular knife-edge1156 is formed at the periphery.

FIG. 34D shows in schematic perspective the circular taperedcross-section light guiding plate 1160 that results from executing theradial extrusion illustrated in FIG. 34C.

FIG. 34E is a schematic perspective view illustrating the correspondingradial extrusion process for facetted cross-section 1162 andcross-section normal 1164 sweeping about axis line 1148 and circularguide path 1152 to form radially facetted light extraction film 1166according to the present invention. Central hole 1168 facilitatesincorporation of an LED emitter and a corresponding light reflectorderivative of the etendue-preserving RAT reflectors (or functionallyequivalent optic) described above.

FIG. 34F is a topside schematic perspective view illustrating the radiallight extracting film 1166 that results from executing the radialextrusion illustrated in FIG. 34E. Central hole 1168 facilitatesincorporation of an LED emitter and a corresponding light reflectorderivative of the etendue-preserving RAT reflectors described above.

FIG. 35A is a cross-sectional perspective view illustrating radiallyfacetted light extracting film 1166 of FIG. 34E and circular lightguiding plate 1160 of FIG. 34D combined in accordance with oneadditional form of the present invention. Light entering cylindricalboundary surface 1154 flows radially through the body of plate 1160,interacts with radially facetted light extraction film 1166 in eachcross-section just as it did in the equivalent cross-section of FIGS.11A-11C, and is output from the circular plate's unobstructed surface1157 along system's Z-axis 6, as equally well-collimated illumination.Layer 1172 is the functional equivalent of optical coupling adhesive 118as shown for example in FIG. 3B or 320 as shown in FIGS. 11C-11D. Inthis example of the present invention, the faceted light extraction film166 has been attached for convenience to the plane (or flat) side of thetapered light guiding plate 1160. It may be attached to either sidewithout performance penalties.

FIG. 35B is a cross-sectional perspective view illustrating the internaldetails of one example of a practical combination of illustrative LEDemitter 1000 (as in FIG. 31A) with radial light guiding system 1170 ofFIG. 35A. The linear light guiding system embodiment of FIGS. 31A-31Bused etendue-preserving RAT reflector 1004 as its means of lightcoupling from LED emitter 1000 to linear light guiding plate 1034. Theone sided radially symmetric equivalent of linearly emitting RATreflector 1004 is radially symmetric (angle transforming) reflector1174. The packaging of Osram's six-chip OSTAR™ model LE CW E3Anecessitates using a one sided reflector. Sidewall curvature 1178 ofreflector 1174, like that of RAT reflector 1004, is driven by theboundary conditions of etendue-preserving equations 10-15, and isthereby related to the linearly extruded sidewall shape of RAT reflector1004, as in FIG. 31C. The shape of reflector 1174 is meant to beillustrative of its general form and may be implemented in a variety ofmetal, metal-coated dielectric and total internally reflectivedielectric formats. Similarly, the plane cylindrical input face 1154 oftapered light-guiding plate 1034 is also only one example. It may bepreferably curved or facetted in some situations, and the taper planemay also be varied in shape nearest input face 1154 as a result.

FIG. 35C is a magnified view 1180 of cross-section of FIG. 35B showingfiner details of the light input region of this illustrative radial formof the thin emitter-reflector-light guiding plate illumination system.The process of light transmission and light extraction was explainedearlier (e.g., FIGS. 11A-11C and 12B) and applies without modification,to the radial form, as each radial cross-section remains that of FIG.11A. For convenience, a few illustrative rays 1181-1187 are shown in thecross-sectional plane. With DC operating voltage applied to terminals1062 of LED emitter 1000, ray 1181 is emitted outwards from one of theemitter's six LED chips. This illustrative ray strikes the reflectingsidewall curvature 1178 of radial angle transforming reflector 1174, andas did RAT reflector 1004, redirects ray 1181 as ray 1182 towardscylindrical entrance face 1154 of the light guiding plate 1160. Theradial transforming reflector 1174 may be replaced by other functionallysimilar coupling optics, including one or more of circularly symmetricreflectors of different surface curvature than 1178, one or morecircularly symmetric reflectors of with segmented surfaces, a lens, agroup of lenses, a refractive reflector, a light pipe section, ahologram, a diffractive film, a reflective polarizer film, and afluorescent resin. Furthermore, the LED emitter 1000 may have adifferent form of light-emitting surface than that shown (the lightemitting surface shown being the flat exterior surface of a clearencapsulent surrounding the LED chips), such as a raised phosphor,raised clear encapsulent, raised phosphor or clear encapsulent withmicro-structured exterior surface, or raised phosphor or clearencapsulent with macro-structured surface, said different form allowingmore total emitted light and/or more effective light collection byreflector 1174 or its coupling optic equivalent. Such a differentlight-emitting surface may also be a secondary optic coupled to theclear encapsulent around the LED chips, such as, for example, a domelens like those commonly provided by OSRAM and many other LEDmanufacturers (as mentioned above).

On entry, illustrative ray 1182 becomes propagating ray 1183 and thenpropagating ray 1184 which with similarity to ray path 330-332-334-336in FIG. 11A, generates extracted output ray 1185 (which escapes taperedlight-guiding plate 1160 into air at point 1190 on the plate's outersurface 1157. Remaining light energy continues to propagate withintapered light guiding plate 1060 by total internal reflection asillustrative ray segments 1186 and 1187.

FIG. 36A is a partial cross-sectional perspective view revealinginternal details of the thin emitter-reflector-light guiding plateillumination system 1 elements of FIG. 35A, but along with an example ofone type of radial heat extracting element 1192 useful in suchconfigurations. Thickness 1194 of radial heat extracting element 1192 isonly meant illustratively, and depends on the operating wattage of LEDemitter 1000, the efficiency with which sink and emitter substrate arethermally attached, the sink material, the dynamics of ambient airflow,and the details of the extracting element's thermal design. The diameter1196 of this particular light engine example of the present invention ischosen as 95.25 mm (3.75 inches), which is a common diameter fortraditionally circular light bulbs. The central coupling diameter 1198in this example, 7.2 mm, has been matched to the characteristics of thesix-chip Osram OSTAR™ model LE CW E3A being used as an example, andcould be made smaller or larger with other LED emitter designs andcoupling arrangements.

FIG. 36B is a schematic perspective view of the illustrative lightengine embodiment represented in FIG. 36A, without the cross-sectionaldetail of FIG. 36A, and in a down-lighting orientation. This perspectivereveals an illustrative means of providing insulated tubular electricalconduit 1200 for electrical interconnections to and from the interiorterminals 1062 of LED emitter 1000, and the associated electricalconnecting pins 1202 and 1203. Tubular conduit 1200 may be substantiallyhollow, and may be an integral part of heat extracting element FIG. 36Cis a schematic perspective view similar to that of FIG. 36B showing theillustrative light engine embodiment of FIGS. 35A-35C and 36A-36B andit's intrinsically well-collimated far-field output illumination 1206.Computer ray trace simulations of this design show a circular beamprofile 1208 in the far field with angular extent 1210, +/−θ_(c) beingapproximately +/−6-degree (FWHM), with a soft halo out to about+/−9-degrees.

FIG. 36D is an exploded perspective view of the light engine representedin FIG. 36B, adding parabolic lenticular film sheets (1212 and 1213)plus a circular frame 1214 to retain them. The parabolic lenticular lenssheets 1212 and 1213 are the same orthogonally-crossed angle-changingelements described earlier (e.g., film elements 874 and 875, FIG. 28)with the lenticules of each film sheet 1212 and 1213 preferably facingtowards the light engine's output surface 1157. Circular frame 1214 isadded to retain the two sheets. In this example, linear extruded filmsheets 1212 and 1213 are cut into circular disks for easiest mounting.

FIG. 36E shows the unexploded view of the thin system 1 of FIG. 36D.

FIG. 36F is a schematic perspective view similar to that of FIG. 36C butshowing the asymmetrically widened far field output illumination 1220 ofthe thin illumination system 1 shown in FIG. 36E. Computer ray tracesimulations of this design, show that the addition of the two crossedlenticular angle changing films of the present invention, in thisexample each having deliberately different angle-changingcharacteristics (one widening the intrinsic +/−6-degree illumination to+/−30-degrees in the ZX meridian, and the other widening the +/−6-degreeillumination to only +/−15-degrees in the orthogonal ZY meridian)produce the intended substantially rectangular beam profile 1222 in thefar field with angular extents 1224 and 1226, +/−θ_(X) beingapproximately +/−30-degree (FWHM), with practically no halo beyond that,and +/−θ_(Y) being approximately +/−15-degree (FWHM), with practicallyno halo beyond that. In this form of the present invention, the crossedlinear extruded lenticular lens sheets 1212 and 1213 (hidden in FIG.36F, transform the circularly symmetric near field light 1228 intorectangular far field light 1222.

FIG. 36G shows the illustrative far field beam pattern from the thinillumination system 1 of FIG. 36F placed at a 1500 mm height above the1800 mm×1800 mm surface to be illuminated. The computer simulated fieldpattern 1230 spreads about +/−30-degrees along x-axis 7+/−15-degreesabout y-axis 5, both FWHM.

All examples of the present thin illumination system invention utilizeone or more low-voltage DC operating LED emitters as their internalsource of light. It is feasible to use any of the foregoing light engineexamples (e.g., FIGS. 1A-1D, 2A-2E, 3A-3B, 4, 12B-12C, 26, 28, 30A, 30C,31A-31B, 32A-32B, 33A-33C, and 36B-36F) with a high voltage AC powersource, provided the high voltage AC power source is properly convertedto low-voltage DC and suitably regulated, prior to its interconnectionwith LED emitters 3, 904 and 1000 of the present invention.

A potentially practical commercial reason for doing this is presented bythe light engine example of FIGS. 36B-36F. Such a thin circulardirectional illumination system when fitted with a suitable AC-to-DCconverting stem attachment terminated with standard light-bulb stylescrew cap, may be deployed usefully as a screw-in retrofit type LEDlight bulb. The far field illumination from all thin light engines madeaccording to the present invention, exhibits particularly sharp angularcutoff outside the intended angular extent. This behavior is associatedgenerally with reduced off-angle glare and more efficient fieldutilization preferred in light bulbs used in spot and flood lightingapplications.

FIG. 37 is a schematic perspective view illustrating one possible way ofadapting the thin profile light engine example of FIG. 36E as a screw-instyle light bulb. In this illustration, the necessary AC-to-DCconversion electronic parts are housed (and not shown) within adapterstem 1232. Adapter stem 1232 is thermally coupled to radial heatextracting element 1192, electrically interconnected to insulatedtubular electrical conduit 1200 and fitted with standard light bulbstyled screw cap 1234. The thin profile light engine example of FIG. 36Emodified only with decorative bezel and affixation hardware may beapplied directly in conventional recessed can applications.

The radially constrained extrusion of tapered light guiding plate 1160,as described by FIGS. 34C-34D, leads to the circular light guiding plategeometries illustrated. It is both possible and practical, however, toconvert the circular light guiding plate form of the present inventioninto a related square and rectangular form. The linearly extruded squareand rectangular light guiding plates 112 and 1034 used in the lightengine examples of FIGS. 30A, 30C, 31A-31B, 32A-32B, and 33A-33C musthave a linear LED emitter input coupling means, which in turn extendsthe resulting light engine's lateral dimensions proportionally. Theradial form described by FIGS. 36A-36F serves to encapsulate the LEDemitter between the tapered light guiding plate and the heat extractor,which is a desirable feature.

Unfortunately, simply trimming the circular light guiding plate to asquare or a rectangle form, sacrifices a substantial percentage of lightoutput efficiency. The reason for this truncation inefficiency can beseen in the illustrations of FIGS. 38A and 38B.

FIG. 38A is a schematic perspective view of a square truncation 1240 ofthe radially constrained light guiding plate extrusion illustrationshown previously in FIG. 34C. It can be seen that many of the taperedcross-sections are clipped off prematurely by this truncation beforethey can reach their full taper length when the taper becomes anidealized knife-edge like those in the linear extrusions of FIG. 34A orthe radial extrusions of FIG. 34C. In the truncation of FIG. 38A, idealcross-sectional behavior only occurs on the diagonals of the inscribedsquare. Elsewhere, the tapered cross-sections are clipped off earlier.The consequence of having truncated cross-sections in an efficientlymade light guiding plate is undesirable light loss from thickened edgesof the truncated plate.

FIG. 38B is magnified section view 1242 of the complete schematicperspective provided in FIG. 38A, better illustrating the significanceof edge-thickening defects caused by premature truncation. It is readilyseen that tapered cross-section 1244 come to almost an ideal knife-edge,but that tapered cross-section 1246 is truncated to substantiallygreater edge thickness 1248.

The remedy for this inefficient taper truncation is a straightforwardcombination of radial and linear boundary constraints, enabled by avariable taper length and taper angle. Rather than forcing the tapercross-section to remain constant in length (and associated taper angle),both the taper length and angle are permitted to vary subject tocorresponding radial and linear extrusion constraints. In this manner aradially extruded square (or rectangular) light guiding plate joinslight guiding plates of the present invention.

FIG. 39A illustrates a radially and linearly constrained extrusion withfive prototype taper cross-sections 1250-1254, swept in a 90-degreeradial arc segment 1256 about axis line 1148 (running parallel to systemZ-axis 6). While the taper cross-sections sweep radially about axis line1148 and arc 1256, their zero-thickness idealized knife-edges areconstrained to follow linear extrusion axis 1258.

FIG. 39B is a perspective view illustrating the extrusive combination offour of the 90-degree segments as developed in FIG. 39A.

FIG. 39C is a perspective view, similar to that of FIG. 34D, butillustrating the quad-sectioned square tapered light guiding plate 1260that results from the radially and linear constrained extrusion of FIG.39C. This square light guiding plate 1260 is radially fed with LEDemitter input light through the same cylindrical entry surface 1154 asdeveloped for circular light guiding plate 1160 in FIG. 34D.

An alternative embodiment of the present invention, very much resemblingthe quadrant shown in FIG. 39A is produced by linearly extruding crosssection 1252 along Y-axis 5 in both directions (as if creating arectangular plate) and then chopping it along the planes defined by 1254and 1250. This extrusion would by default create a linear input facerather than one curved about axis 1148, though the input face could beeasily made curved by simple cut-out. Four of these quadrants could thengo together just as in FIGS. 39B-39C, with somewhat simpler surfacetopology but still meeting the knife edge requirement required formaximum efficiency and still having similar appearance.

Another embodiment of the present invention uses just the one quadrantof FIG. 39A combined with a source and coupling optic that send lightsubstantially into the input face of that one quadrant.

Yet another embodiment of the present invention can be created simply bybifurcating the quadrant of FIG. 39A at the plane defined by crosssection 1252, creating two substantially triangular half-quarters, andjoining the two half-quarters at the surfaces defined by 1250 and 1254to create one square quadrant (as opposed to the triangular quadrantshown). This can be combined with a source and coupling optic that sendlight substantially into the input face of that one quadrant.

In each of the latter three embodiments, the plates can be combined withsubstantially the same circular turning films (cut to size) introducedin FIGS. 34E-34F to produce highly collimated light. While thecollimated far-field pattern in each case will not be identical to thatof the circular disk of FIG. 35A-35C, the use of previously discussedbeam-spreading films (e.g. shown in 36D) can produce substantially manyof the same far-field patterns possible with the other linearly andradially extruded engines described above.

FIG. 39D is a perspective view of a thin square light engine form of thepresent invention that uses a square lighting guiding plate 1260(hidden), and an otherwise similar internal arrangement to that of thecircular light engine example shown in FIG. 36E. Square cut lenticularfilm sheets 1262 are retained in frame 1264. Radial heat extractingelement 1192 is deployed in this example as square heat extractingelement 1266. While embodiments of the present invention based onradially extruded light guiding plates and light extraction films areuseful, there is one illumination attribute that's unique to thelinearly extruded light guiding and light extracting forms describedabove. The linearly extruded light guiding systems (e.g., thoserepresented in FIGS. 3A-3B, 4, 26, 28, 30A, 30D, 31A, 31D, 32A-32B, and33A-33C) have the capacity to provide collimated illumination at anoblique angle to the light guiding plane, potentially providing anunobtrusively compact means of oblique illumination.

FIG. 40A shows a perspective view of another embodiment of thesingle-emitter form of the thin illumination system 1 deploying atapered light guiding pipe system 120 as its input engine that iscross-coupled with tapered light guiding plate system 1992 using a planetop mirror 1990. A generalized description of tapered light guidingsystem 1990 was shown earlier in FIG. 3A as 110 with a facetted lightextraction film. In this particular example, the system's facettedreflecting prisms 116 (as in FIG. 3A) are replaced with a specularlyreflecting plane mirror 1990. This modification is equivalent to makingthe total included apex angle 352 of the reflecting prisms used in FIG.3A and described in the details of FIG. 11A approach 180-degrees.

FIG. 40B is a side cross-sectional view of FIG. 40A, similar to thatshown earlier in FIG. 8B, except that FIG. 8B applied only to the inputengine, collimating light in just the one meridian shown. The presentembodiment collimates output light in both meridians, and along with useof optimized input light 1994 (in air) and 1996 (in light guide 112)from RAT reflector 114 (illustratively +/−52.5-degrees in air) theoverall illumination system 1 develops a more smoothly shaped far fieldoutput beam profile 1998. All dimensions and materials follow thepreviously established ongoing example, which set illustrative 3 mmplate thickness (THKP 156) and illustrative 3 mm pipe thickness (THKB150), both as in FIG. 4, 3-degree pipe and plate taper angles,approximately 50 μm knife edge thickness, polycarbonate pipe 100 andpolycarbonate plate 112 (which as described above, may be preferablymade of PMMA). Reflector 1990 is attached to the illustrative 57 mm×57mm tapered light guiding plate 112 as discussed earlier, by an acryliclayer having refractive index between 1.47 and 1.49.

FIG. 40C is a perspective view of the illumination system of FIGS.40A-40B showing the collimated nature of the obliquely directed farfield output beam the system produces. Dotted outline 2010 helps invisualizing the beam character.

FIG. 41A is a side elevation showing the deployment of the illuminationsystem 1 of FIGS. 40A-40C mounted a vertical distance of 10 feet (about3000 mm) 2020 above ground level 1022 and a horizontal distance of 3feet (about 900 mm) 2024 from a vertical wall surface 2026 to beilluminated by the obliquely-directed far field output beam 1990 comingfrom this type of thin-profile illumination system 1. The associatedbeam pattern on wall surface 2026 is displaced downward from theluminaire system's horizontal mounting plane by 1.82 feet (about 550 mm)2028 because of the approximately 27-degree beam direction establishedin FIG. 40B (for the illustrative conditions).

FIG. 41B shows a front view of wall surface 2026 and beam pattern 2030made by illumination system 1 of the present example. Beam pattern 2030retains its approximately +/−5-degree angular extent in the horizontalplane, but is broadened in the vertical direction to about +/−10-degreesby the projection caused by its oblique angle of incidence. Theassociated horizontal and vertical brightness profiles are designated2032 and 2034.

FIG. 42 is a perspective view of another embodiment of the presentinvention similar to FIG. 31C, but adding one variation, the applicationof a one-dimensional angle-spreading lenticular filmstrip 1036 to inputedge 121 of light guiding plate 112 to widen the outgoing beam's 2038horizontal angular extent.

FIG. 43A illustrates the side elevation of a wall and floor systemincluding the illumination system of FIG. 42. It further illustratesthat despite the addition of angle-spreading film 2036 to the input edgeof light guiding plate 112, the obliquely directed far field beam crosssection 2038 and the rest of the side elevation layout, is identical tothat of FIG. 41A in this example.

FIG. 43B shows a front view of wall surface 2026 and beam pattern 2040made by illumination system 1 of the present example. Beam pattern 2040is broadened in the vertical direction to about +/−10-degrees, asbefore, by the projection caused by its oblique angle of incidence, buthas been broadened deliberately to +/−24-degrees as shown by thelenticular angle-spreading film that is used. The associated horizontaland vertical brightness profiles are designated 2042 and 2044.

FIG. 44 is a side view of yet another embodiment of the presentinvention, one based on the inventive variations of FIGS. 40A-40C, 41A,42 and 43A, but adding an external tilt mirror, 2050, to receive theobliquely-directed output illumination 1998 (or 2038) from thisvariation of illumination system 1, and redirecting that illumination2038 back towards another vertical surface 2052 to be illuminated, as inredirected beam profile 1052. The mathematical relationship between allelements is based on straightforward geometry, and the necessary symbolsare provided clearly on FIG. 44 in full detail. The mirror length(BD+DF), LM, is determined by the extreme field angle, β_(f), which forthe present example is xxxβ_(f)=θ_(W)+Å_(b), Å_(b) being the extractedbeam's half width, 32.8-degrees. Length BC=LP (Tan β_(f)). Offset lengthCE=LP (Tan β_(f)) Tan γ_(T), CD=BC (Sin γ_(T)). BD=BC (Cos γ_(r)). Thenin triangle CEF, the third angle is 180−β_(f)−(90+γ_(T))=90−β_(f)−γ_(T).So, DF=CD (Tan 90−β_(f)−γ_(T)). And, LM=BD+DF=(BC)(Cos γ_(T))+(BC(Sinγ_(T)))(Tan 90−β_(f)−γ_(T))=LP Tan(β_(f)) [Cos(γ_(T))+Sin γ_(T)Tan(90−β_(f)−γ_(T))]. The numerical values shown in FIG. 44 are for anillustrative mirror tilt, γ_(T), of 12-degrees.

The degree to which tilt mirror 2050 is tilted with respect to thesystem's vertical z-axis 6, γ_(T) above, and the separation distance2054 between the system's tilt mirror and the surface to be illuminated,collectively determine how far down the opposing vertical surface willthe resulting illumination pattern be situated.

FIG. 45A is a side elevation showing the deployment of this variation onillumination system 1 mounted 10 feet above ground level 2022 and ahorizontal distance of 3 feet from a left hand vertical wall surface2060 to be illuminated by the obliquely-directed far field output beam2062 coming from this tilted-mirror version of this thin-profileillumination system 1. The associated beam pattern 2064 on wall surface2060 is displaced downward about 3.7 feet from the luminaire system'shorizontal mounting plane because of the 12-degree tilt placed on tiltmirror 2050. The resulting pattern shift for this 12-degree tilt isapproximately 3 Tan(2γ_(T)+φ_(W))=3 Tan(51)=3.7 feet.

FIG. 45B shows a front view of left-side wall surface 2056 and beampattern 2070 made by illumination system 1 of the present example. Beampattern 2070 retains its horizontal plane broadening from lenticularinput film 2036, but shifted downward by the action of tilt mirror 2050and its 12-degree tilt in this example. The associated horizontal andvertical brightness profiles are designated 2072 and 2074.

FIG. 46A is a side elevation identical to FIG. 45A, but for the case ofa 16-degree mirror tilt. The associated beam pattern 2080 on wallsurface 2060 is displaced downward about 5 feet from the luminairesystem's horizontal mounting plane because of the 16-degree tilt placedon tilt mirror 2050.

FIG. 46B is the same representation as FIG. 45B, but for the case of a16-degree mirror tilt and its associated beam pattern 1080. Theassociated horizontal and vertical brightness profiles are designated2082 and 2084.

FIG. 47 is a perspective view of the corner of a room, showing twowalls, a floor, and a framed painting illuminated obliquely by thethin-profile tilted mirror illumination system of the present inventionfor the case illustrated in FIG. 46A-B representing a 16-degree mirrortilt.

The embodiments shown in FIGS. 40A-40C, 41A, 42, 43A, 44, 45A, 46A and47 represent just one of numerous possible examples. Rather than usingplane mirror 1990 (FIG. 44), in combination with tilted mirror 2050(FIGS. 44, 45A and 46A), faceted prism sheet 114 could be arranged withthe equivalent facet angles to generate the same illuminating outputbeam direction (via the beam redirecting inventions of FIGS. 11A-B, 18,19 and 20). Moreover, the multi-element array-type input engine (FIGS.2A-C, 31A-31B, 32A-32B, and 33A-33C) may be substituted whenapplications call for higher lumen output from a single luminaire unit,as they might in various high intensity spot lighting uses, or adifferently arranged grouping of light engines facilitated byindividualized LED emitter engine segments.

FIG. 48A shows yet another an embodiment of the present inventionsimilar to that of FIG. 42, adding a one-dimensional angle-spreadinglenticular filmstrip 2036 to input edge 121 of light guiding plate 112to widen the outgoing beam's 2100 horizontal angular extent, but using aprism sheet rather than a plane mirror atop tapered light guiding plate112.

FIG. 48B shows the configuration of FIG. 48A in perspective view.

FIG. 48C is another perspective view of FIG. 48A, showing theillumination system's underside output aperture, along with itsresulting near field spatial brightness uniformity 2104 and the darkfield area 2106 occurring nearest the beginning region of its LED inputengine.

FIG. 49 is a perspective view isolating on the behavior of thetapered-version of the light guiding input engine 120, showing graphicsimulation 2110 of angular extent of the light condition at the start oflight guiding pipe 100, and a graphic simulation sequence 2111-2115 ofthe subsystem's output light at various points along the light guidingpipe's output edge. It can be seen that despite the optimum choice ofthe angular distribution of input light at the start of the lightguiding pipe, the subsystem fails to maintain constancy of the outputlight angular extent. Output light nearest the start of the lightguiding pipe shows a substantially reduced angular range, and doesn'tstabilize the expected angular distribution until nearly the midpoint.This misbehavior (or deviation from ideality) gives rise to the nearfield non-uniformity shown in FIG. 48C.

One solution to the near field spatial non-uniformity comes from theinvention of FIGS. 42 and 48A-48B. These illustrations showed that thedeployment of a lenticular lens sheet, lens axes aligned perpendicularlyto the long length of the light guide plate's edge, is successful inwidening the outgoing beam's corresponding angular extent. It stands toreason that because of this, smaller portions of lenticular lens filmmay be applied to boost the angular content of a deficient angular widthjust enough to make it right.

FIGS. 50A-50B, 50D, 50F and 50G all show various lenticular film sectionconfigurations that have been simulated. In each case, not only has thesize and shape of the lenticular section been varied, but so has thestrength (optical power) of the parabolic lenticules.

The success of this idea in improving the evenness of near fielduniformity is demonstrated in the perspective views FIGS. 50E and 50H.The optimization shown in FIGS. 50A-50D, 50F and 50G all show variouslenticular film section configurations that have been simulated.

For specialty applications such as LCD backlighting, where visualappearance of the near field illumination is more critical, improvementssuch as are summarized in FIGS. 51A-51C are available as well. In thissequence, the spacing of the prisms in light extraction film applied tothe light guiding plate is adjusted to fine tune the degree of nearfield spatial non-uniformity.

FIG. 51A shows the underlying concept of this variable prism spacingmethod, using a conveniently enlarged prism coarseness to help displaythe design intent. The bands without prisms do not extract output light,and can be used to dilute regions having excess brightness. Since prismperiods are best below the levels of visual acuity, the use of darkbands will not interfere with viewing quality.

FIG. 51B shows a perspective view of the design concept illustrated inFIG. 52A.

FIG. 51C shows a perspective view of a thin illumination system 1 of thepresent invention with successfully homogenized near field using thevariable prism spacing method.

FIG. 52 shows a graphical comparison of near field spatialnon-uniformity of one thin profile illumination system partiallysuccessful angular input edge correction as in FIG. 50H and one with thecomplete correction illustrated in FIG. 51C via the variable-prismspacing-method. A graphic simulation of the near field uniformity 2146shows considerable smoothness compared with simulation 2130 if FIG. 52E.While preferred embodiments of the inventions herein have been shown anddescribed, it will be clear to those of skill in the art that variouschanges and modifications can be made without departing from theinvention in the broader aspects set forth in the claims hereinafter. Inparticular, the various subcomponent elements and systems describedherein, as well as their optical equivalent, can be used in combinationwith, or when operatively proper substituted for, the other elements andsystems set forth herein.

What is claimed is:
 1. An illuminating system, comprising: a single LEDemitter having a square or rectangular emitting aperture that is d1 byd2, a four sided etendue preserving angle transforming reflector whoseinput aperture is disposed just above the output emitting aperture ofsaid single LED emitter receiving LED emission, a light guiding pipewhose input aperture receives light from the output aperture of saidetendue preserving angle transforming reflector element, a light guidingplate one edge of which is disposed adjacent to said rectangular edge ofsaid light guiding pipe.
 2. The illuminating system as defined in claim1 wherein said rectangular four sided etendue preserving angletransforming reflector transforms the LED's wide angle output emissionto output light passing through its output aperture in both meridians ofthe light guiding pipe with an angular extent substantially equaling+/−θ, where +/−θ is determined by the applicable etendue preserving SineLaw, θ=Sin⁻¹(d_(i)/D_(i)), where D_(i) and d_(i) refer to the input andoutput aperture dimensions in each meridian.
 3. The illuminating systemas defined in claim 2 where θ (in air) is between 50-degrees and55-degrees in each meridian.
 4. The illuminating system as defined inclaim 1 having one or more lenticular lens sheets disposed beyond saidrectangular output face, their lenticules facing towards saidrectangular output face
 5. The illuminating system as defined in claim 4wherein said one or more lenticular lens sheets containparabollically-shaped lenticules.
 6. The illuminating system as definedin claim 4 wherein said one or more lenticular lens sheets are orientedwith respect to each other such that their lenticular lens axes aresubstantially orthogonal to each other.
 7. The illuminating system asdefined in claim 1 having one or more conventional diffuser sheetsdisposed beyond said rectangular output face.
 8. The illuminating systemas defined in claim 1 having said input aperture of said light guidingplate covered completely or partially by a lenticular lens film whoseplane surface is disposed towards said input aperture and whoselenticular lens axes are aligned either parallel to the edge of saidinput aperture, or perpendicularly to the edge of said input aperture.9. The illuminating system as defined in claim 1 with a tilted planemirror disposed to receive said output beam and redirect it in adifferent angular direction.
 10. The illuminating system as defined inclaim 1 whose first prismatic lens sheet contains a substantiallycontinuous array of prism lenses each having left hand reflecting facetsand right hand reflecting facets, said right hand facets receivingsubstantially all the incident light.
 11. The illuminating system asdefined in claim 10 where the total included angle between said righthand facets and said left hand facets is in the range 95 to 105 degrees.12. The illuminating system as defined in claim 10 where the angle madeby said right hand facets and the normal to the prism base is in therange of 58-degrees and 63-degrees.
 13. The illuminating system asdefined in claim 1 whose second prismatic lens sheet contains asubstantially continuous array of prism lenses each having left handreflecting facets and right hand reflecting facets, said right handfacets receiving substantially all the incident light.
 14. Theilluminating system as defined in claim 13 where the total includedangle between said right hand facets and said left hand facets is in therange 75 to 120 degrees.
 15. The illuminating system as defined in claim13 where the angle made by said right hand facets and the normal to theprism base is in the range of 58-degrees and 63-degrees.
 16. Theilluminating system as defined in claim 13 where the angle made by saidright hand facets and the normal to the prism base is in the range of40-degrees and 80-degrees.
 17. An illuminating system, comprising: alinear array of LED emitters whose center-to-center distance betweenemitters is W, and each having a square or rectangular output aperturethat is d1 by d2, a substrate circuit with electrical interconnectionmeans for said array of LED emitters, a linear array of rectangular foursided etendue preserving angle transforming reflectors whose rectangularinput apertures are d1 by d2 and have a center-to-center spacing W, witheach said input aperture disposed just above said output aperture ofeach said LED emitter in said array, a light guiding plate one edge ofwhich is disposed adjacent to said rectangular edge of said lightguiding pipe.
 18. The illuminating system as defined in claim 17 whereineach of said rectangular four sided etendue preserving angletransforming reflector in said array of said rectangular four sidedetendue preserving angle transforming reflectors collimates its outputlight through its D1 sized output apertures in the meridian parallel tothe long axis of said rectangular edge of said light guiding pipe withan angular extent in said meridian substantially +/−θ1, where +/−θ1 isdetermined by the applicable etendue preserving Sine Law, with θ1substantially Sin⁻¹(d1/D1).
 19. The illuminating system as defined inclaim 18 wherein each of said rectangular four sided etendue preservingangle transforming reflectors in said array of said rectangular foursided etendue preserving angle transforming reflectors has its opposingsidewalls shaped mathematically according to the boundary condition ofpreserving etendue between input aperture and output aperture.
 20. Theilluminating system as defined in claim 19 wherein each of saidrectangular four sided etendue preserving angle transforming reflectorsin said array of said rectangular four sided etendue preserving angletransforming reflectors has total designed length of 0.5(d1+D1)/Tan(θ1),but which may be trimmed back from said designed length leaving 40% ormore of said designed length remaining.